1. Add basic metrics for data operation in storage service
2. Add a storage integrity test tool in storage-perf.

close #287

Now we support following metrics: get_bound, bound_stats, vertex_props, edge_props, add_vertex, add_edge, del_vertex, update_vertex, update_edge.

We can get qps or latency from these metrics (add suffix), for example: vertex_props_qps or vertex_props_latency.

You can get a single metrics like this:
curl -G "http://127.0.0.1:50005/get_stats?stats=vertex_props_qps.rate.60

If you want get multiple metrics like this:
curl -G "http://127.0.0.1:50005/get_stats?stats=vertex_props_qps.rate.60,vertex_props_latency.avg.60,vertex_props_latency.p99.60&returnjson"
We can get qps, avg latency and p99 latency in a minutue.

You can get all metrics like this:
curl -G "http://127.0.0.1:50005/get_stats?stats"

The storage integrity tool is used for verifying data integrity in storage. It only works for single replica for now. You can use it like this:
./storage_integrity --meta_server_addrs=192.168.8.5:60001 --first_vertex_id=100 --width=1000 --height=1000

meta_server_addrs is the meta server addresss.
first_vertex_id is the first vertex id which we inserts.
width and height is the width and height of the big matrix.

* docs for RC1

* add limit

* add string operations

* fix minor

* update readme, and remove index.md

* add changelog.md

* move introductions to overview directory
fix space

* rebase master since Sep16

* fix bilibili address

* address laura's comment

* Fix fail to delete the vertex without edges

* add UT

1 When multiple statements contain empty statements.
2 When the function is called, if the first parameter of the parameter list is empty.

for example:
  ";MATCH"
  "floor( ,1)"

* modify verify kv

* invalidate leader when E_PART_NOT_FOUND returned

* fix balance data failed from one replica
build simple_kv_verify as a independent package

* enhance balancer

* Fix failed balancer_test

Add more ignored files for docker and exec clang-format before commit

* show space name in leader/part distribution of show hosts

* update

* fix space lock

* update

* address yixinglu's comments

* fix @wadeliuyi's comments and update docs

* fix crash when balance leader timeout

* support general storage in StorageService

* fix nebula benchmark crash

* Simple KV Verify Tool

* support uuid

* support uuid

* increase storage client

* Implement member change

* Address wadeliuyi's comments

* Add Balance UT

* Fix failed Meta http Uts

* Add balance data and balance data id command in console

* Fix bugs

* Fix stale peers when add part

* Fix bugs

* Remove retry logic and fix stale log response

* Address cirtical27's comments

* Fix snapshot_test

* Fix bug in snapshot

* Remove check in commitTransferLeader

* support nebula key type

* modify key structure

* update commit key

* use kSystem

* Fix giving wrong column names when union has only right result.

* Move index out explicitly.

* Add tests.

* Address @wadeliuyi's comment.

* Rebase and fix conflict.

* Address comment.

* Improved build concurrency

* Depend on parser

* Addressed @yixinglu's comment

* Fixed issue when ASAN enabled

Now, we support updating one vertex or edge with constraints， all operations about read-modify-write are atomic.

The filters and yields expressions in update sentence will be pushed down into storage layer.

* Support to package  as one deb/rpm

* Rebase master

this problem was caused by the conversion of decimal to hexadecimal when the console prints the VID type.

*     Issue#192 Support multiple edge types in GO statement

Summary:
Implemented over multiple edge types(include over "*" ) for Support all edge type in Go statement.

1. Modification of the storage interface:
   1.1 Modify the GetNeighborsRequest structure, pass a list of edge_type to the storage layer.
   1.2 And add an over_all_edges tag to mark "over *".
       Modify the PropDef structure to represent both tag_id and edge_type
   1.3 Added the EdgeData structure to represent the edge data returned to the client.
2. When the yield statement does not exist, rename the "_dst" attribute of edge to edge_name+"_id"
3. Delete the getOutBound and getInBound interfaces,
   because the edges passed to the storage may have both in and out.
4  Added a map of edge type to edge name for metaclien (toEdgeName)

PS:
There are still two issues that need to be implemented.
1 Since we are not implementing a null type, we cannot represent some non-existing attributes.
2 Due to the existence of 1, there is currently no judgment on the attributes of the edges and the vetex.
So when returning multiple types of vetex/edge,
the same result will be returned if the attribute names are the same("MULTI_EDGES" test in GoTest.cpp).

* 1. add more test.
2. Solved the problem of display when some properties are not present(return the default value to the user).

for example:
type             default
int              0
bool             false
double/float     0.0

* format the code style.

* 1. When yield does not exist, don't implicitly rename _dst prop.
2. format some code style.

* Fixed an problem where the results might be incorrect when using multiple edges with filter.

* Modify the storage interface to move the schema from tagdata/edgedata to QueryResponse.

* Address dangleptr's and wadeliuyi's comments.

*  Address dangleptr's and laura's comments.

* Address laura's comments.

*      Address dangleptr's comments.

* Address dangleptr's comments.

* Address dangleptr's comments.

* fixed the unit test failed(go_test and orderbytest).