Summary: Most of the approach is copied from WebSQL's MySQL branch. It's nice that we can do this without touching core RocksDB code.
Test Plan: Compiles and runs. Didn't test flashback code, as I don't have flashback device and most if it is c/p
Reviewers: MarkCallaghan, sdong
Reviewed By: sdong
Subscribers: rven, lgalanis, kradhakrishnan, dhruba, leveldb
Differential Revision: https://reviews.facebook.net/D35391
