Shortest path and all paths (#847)

* Add find path sentence.

* Add getFrontiers.

* Add findPath.

* Update visited vertex.

* Consider even length path.

* Add test no filter.

* Refactoring. Add tuple<id, +/-type, ranking> to indicate a step in a path.

* Support find all path.

* Refactoring the prepare part.

* Add shortest path test case.

* Enhancement with clearing the interim path.

* Verify result with string.

* Enhancement, and print edge in cmdprocessor.

* Add column type of path.

* Building path with ptr(Enhancement).

* Rebase and support multi edges

* Add multi edges test.

* 1. Use high priority for get-neighbors task when find path.
2. Update the formats in console for path.

* Debug: duplicate path found. Solution: clear ids before copy.

* Rebase and solve conflict.

* Remove barrier.

* Rebase and address comment.