Make VersionBuilder unit testable

Summary:
Rename Version::Builder to VersionBuilder and expose its definition to a header.
Make VerisonBuilder not reference Version or ColumnFamilyData, only working with VersionStorageInfo.
Add version_builder_test which has a simple test.

Test Plan: make all check

Reviewers: rven, yhchiang, igor, ljin

Reviewed By: igor

Subscribers: leveldb, dhruba

Differential Revision: https://reviews.facebook.net/D27969
Apply InfoLogLevel to the logs in table/block_based_table_reader.cc

Summary:
Apply InfoLogLevel to the logs in table/block_based_table_reader.cc

Also, add missing checks for the returned status in BlockBasedTable::Open

Test Plan: make

Reviewers: sdong, ljin, igor

Reviewed By: igor

Subscribers: dhruba

Differential Revision: https://reviews.facebook.net/D28005
Turn on -Wshadow

Summary:
...and fix all the errors :)

Jim suggested turning on -Wshadow because it helped him fix number of critical bugs in fbcode. I think it's a good idea to be -Wshadow clean.

Test Plan: compiles

Reviewers: yhchiang, rven, sdong, ljin

Reviewed By: ljin

Subscribers: dhruba, leveldb

Differential Revision: https://reviews.facebook.net/D27711
Add support for in place update for db_stress

Summary:
Added two flags which operate as follows:
in_place_update: enable in_place_update for default column family
set_in_place_one_in: toggles the value of the option inplace_update_support with a probability of 1/N

Test Plan:
Run db_stress with the two flags above set.
Specifically tried in_place_update set to true and set_in_place_one_in set to 10,000.

Reviewers: ljin, igor, sdong

Reviewed By: sdong

Subscribers: dhruba, leveldb

Differential Revision: https://reviews.facebook.net/D28029
Move convenience.h to /include

Summary: Move header file so it can be referenced externally.

Test Plan: Rebuild.

Reviewers: ljin

Reviewed By: ljin

Subscribers: dhruba

Differential Revision: https://reviews.facebook.net/D28095
temporarily remove -Wshadow