[CF] Column family support for LDB tool

Summary: Added list_column_family command and also updated dump_manifest

Test Plan: no

Reviewers: dhruba, haobo

CC: leveldb

Differential Revision: https://reviews.facebook.net/D16419
[CF] Change flow of CreateColumnFamily

Summary:
Previously, we first wrote to the manifest and then created internal data structure.
Now, we first create internal data structure. That way, we can write out internal comparator to the manifest

Test Plan: column_family_test

Reviewers: dhruba, haobo

CC: leveldb

Differential Revision: https://reviews.facebook.net/D16425
SetLogNumber in CreateColumnFamily
[CF] CreateColumnFamily fix

Summary:
This fixes few bugs with CreateColumnFamily
* We first have to LogAndApply and then call VersionSet::CreateColumnFamily. Otherwise, WriteSnapshot might be invoked, writing out column family add inside of LogAndApply, even though it's not really committed
* Fix LogAndApplyHelper() to not apply log number to column_family_data, which is in case of column family add, just a dummy (default) column family
* Create SuperVerion when creating column family

Test Plan: column_family_test

Reviewers: dhruba, haobo

CC: leveldb

Differential Revision: https://reviews.facebook.net/D16443
Set log number for column family
[CF] Small refactor of Recover() and DumpManifest()
Set dropped column family before persisting in the manifest
Fix LogAndApply() group commit
[CF] Rething LogAndApply for column families

Summary:
I though I might get away with as little changes to LogAndApply() as possible. It turns out this is not the case.

This diff introduces different behavior of LogAndApply() for three cases:
1. column family add
2. column family drop
3. no-column family manipulation

(1) and (2) don't support group commit yet.

There were a lot of problems with old version od LogAndApply, detected by db_stress. The biggest was non-atomicity of manifest writes and metadata changes (i.e. if column family add is in manifest, it also has to be in in-memory data structure).

Test Plan: db_stress

Reviewers: dhruba, haobo

CC: leveldb

Differential Revision: https://reviews.facebook.net/D16491