Don't keep managing two rocksdb version

Summary:
Before this diff, there are two places with rocksdb versions. After the diff:
1. we only have one source of truth for rocksdb version
2. we have a script that we can use to get the version that we can use in other compilations (java, go, etc).

Test Plan: make

Reviewers: yhchiang, sdong, ljin

Reviewed By: ljin

Subscribers: leveldb

Differential Revision: https://reviews.facebook.net/D24333
Column family support in RocksJava

This commit includes the support for the following functionalities:
  - Single Get/Put operations
  - WriteBatch operations
  - Single iterator functionality
  - Open database with column families
  - Create column family
  - Drop column family
  - Properties of column families
  - Listing of column families

In addition there is an additional Java sample which can be build
using "make cfsample".

What is not supported currently using RocksJava:
  - Multi Iterator support
  - MultiGet

I decided to file a pull request w/o the missing two features to omit
some merging trouble. I would propose to hand them over to a later point
of time.
Quality improvements
- Replaced all NULL occurences in code with nullptr
- Removed iostream include
Fixed some lint problems
More lint problems fixed
Moved Testing code from Sample to Test.
Fixed line length in Test