Summary:
This diff introduce new table properties that will be written for block based tables
These properties are
  - comparator name
  - merge operator name
  - property collectors names

Test Plan:
  - Added a new unit test to verify that these tests are written/read correctly
  - Running all other tests right now (wont land until all tests finish)

Reviewers: rven, kradhakrishnan, igor, sdong, anthony, yhchiang

Reviewed By: yhchiang

Subscribers: dhruba

Differential Revision: https://reviews.facebook.net/D34269