Summary:
This will enable people using TTL DB to do so with multiple column families. They can also specify different TTLs for each one.
TODO: Implement CreateColumnFamily() in TTL world.
Test Plan: Added a very simple sanity test.
Reviewers: dhruba, haobo, ljin, sdong, yhchiang
Reviewed By: haobo
CC: leveldb, alberts
Differential Revision: https://reviews.facebook.net/D17859
3992aec8fa