Summary:
Add an option --column_family option, so that users can query or update specific column family.
Also add an create column family parameter to make unit test easier.
Still need to add unit tests.
Test Plan: Will add a test case in ldb python test.
Reviewers: yhchiang, rven, andrewkr, IslamAbdelRahman, kradhakrishnan, anthony
Reviewed By: anthony
Subscribers: leveldb, dhruba
Differential Revision: https://reviews.facebook.net/D53265
38e1d7fea3