* 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).

* Resolve java lint problem with soft link of directory.

* Ignore the soft link of directory.

* Add timestamp

* fix vid

* Address dutor's comment

* Address CPWstatic's comment and Add type cast handle in TraverseExecutor

* update

* update feroda deps

* implement delete a vertex

* address the comments of wadeliuyi and dangleptr

* address dangleptr's comments

* address comments of dangleptr and critical27

* address darionyaphet's comments

* Added support to singular forms for STEPS and VALUES

* Make VALUES unreserved

* enhance java client

* fix docs/nGQL-tutorial.md

Basic leader balance for storage, keep trying to trans leader from host with most leader to host with least leader, until all balanced.

Modify/Add two command in console:

1. "show host" will also display total leader count and leader count in each space
2. add command "balance leader", which will try to balance leader between different hosts

* test edge miss

* fix mutli version

* register gflags in meta client

* parse json

* try register at first operation

* address @laura-ding's comments

* fix ut, address comments

* address laura-dings's comments

* address comments

* address @dangleptr's comments, update gflags.json

* address @dangleptr's comments

* Ignore ccls configuration files

* Fix variable syntax document about load_data_interval_secs

* Cleanup unusable load_config_interval_secs configuration option