Summary:
The GraphDbAccessor and KeyIndex APIs can now also return records for the current transaction+command graph state. This is necessary to correctly implement MERGE. The new logic is has increased the MVCC+Accessor related chaos and should be revised when refactoring MVCC (as planned).
Previous index testing was separated into VertexIndex and EdgeIndex testing. This is inappropriate since most of the logic is exaclty the same. Also it was not clearly defined what gets tested via the GraphDbAccessor API, and what directly through the KeyIndex API. This has also been refactored, but it needs additional work (Gleich).
Reviewers: buda, dgleich
Reviewed By: buda, dgleich
Subscribers: pullbot
Differential Revision: https://phabricator.memgraph.io/D306
