Adding Column Family support in db_bench.

Summary:
Adding num_column_families flag. Adding support for column families in DoWrite and ReadRandom methods.
[Igor, please let me know if this approach sounds good. I shall add it to other methods too.]

Test Plan: Ran fillseq on 1M keys and 10 Column families and ran readrandom.

Reviewers: sdong, yhchiang, igor, ljin

Reviewed By: ljin

Subscribers: leveldb

Differential Revision: https://reviews.facebook.net/D21387
Removing BitStream* functions

Summary: I was checking some functions in coding.h and coding.cc when I noticed these unused functions. Let's remove them.

Test Plan: compiles

Reviewers: sdong, ljin, yhchiang, dhruba

Reviewed By: dhruba

Subscribers: leveldb

Differential Revision: https://reviews.facebook.net/D22077
Remove BitStream* tests
Add CuckooHash table format to table_reader_bench

Summary: Make table_reader_bench cover all the three table formats.

Test Plan: Run it using three options

Reviewers: radheshyamb, ljin

Reviewed By: ljin

Subscribers: leveldb

Differential Revision: https://reviews.facebook.net/D22137
Optimize storage parameters for spatialDB

Summary: We need to start compression at level 1, while OptimizeForLevelComapaction() only sets up rocksdb to start compressing at level 2. I also adjusted some other things.

Test Plan: compiles

Reviewers: yinwang

Reviewed By: yinwang

Differential Revision: https://reviews.facebook.net/D22203
Revert the unintended change that DestroyDB() doesn't clean up info logs.

Summary: A previous change triggered a change by mistake: DestroyDB() will keep info logs under DB directory. Revert the unintended change.

Test Plan: Add a unit test case to verify it.

Reviewers: ljin, yhchiang, igor

Reviewed By: igor

Subscribers: leveldb

Differential Revision: https://reviews.facebook.net/D22209