[RocksDB] Support for column families in manifest

Summary:
<This diff is for Column Family branch>

Added fields in manifest file to support adding and deleting column families.

Pretty simple change, each version edit record can be:
1. add column family
2. drop column family
3. add and delete N files from a single column family (compactions and flushes will generate such records)

Test Plan: make check works, the code is backward compatible

Reviewers: dhruba, haobo

CC: leveldb

Differential Revision: https://reviews.facebook.net/D14733
Hotfix the bug in table cache's GetSliceForFileNumber

Forgot to fix this problem in master branch. Already fixed it in performance branch.
Automate the preparation step for a new release

Summary: Added a script that prepares the repo for facebook's new rocksdb release, which will automatically do some necessary work to make sure this repo is ready for 3rdparty release.

Test Plan:
Run this script and observed:

* new version was created (both in local and remote repo) as a git tag.
* build_version.cc was updated
* build_detect_platform was changed so that it won't create any new change.

Reviewers: haobo, dhruba, sdong, igor

CC: leveldb

Differential Revision: https://reviews.facebook.net/D15003
Add clang-format rules

Summary:
The rule file is forked from that in Facebook's repo.

I'll add format file for now and team members can tune the rules later.

In this patch, I made only two changes in order to be consistent with existing coding style

`SpacesBeforeTrailingComments: 2`

`ColumnLimit:     80`

Test Plan: N/A

Reviewers: igor

CC: leveldb

Differential Revision: https://reviews.facebook.net/D15015
[column families] Support to create and drop column families

Summary:
This diff provides basic implementations of CreateColumnFamily(), DropColumnFamily() and ListColumnFamilies(). It builds on top of https://reviews.facebook.net/D14733

It also includes a bug fix for DBImplReadOnly, where Get implementation would be redirected to DBImpl instead of DBImplReadOnly.

Test Plan: Added unit test

Reviewers: dhruba, haobo, kailiu

CC: leveldb

Differential Revision: https://reviews.facebook.net/D15021
Add a hack to build_detect_platform so it works in all types of fb-servers
Refactor build_tools/build_detect_version
Fix issue #57
Merge pull request #56 from sepeth/refactor-detect-version

Refactor build_tools/build_detect_version
Revert change in 8f6e319.
Merge branch 'master' into columnfamilies