Summary:
We have not been updating our HISTORY.md change log with the RocksJava changes. Going forward, lets add Java changes also to HISTORY.md.
There is an old java/HISTORY-JAVA.md, but it hasn't been updated in years. It is much easier to remember to update the change log in a single file, HISTORY.md.

I added information about shared block cache here, which was introduced in #3623.
Closes https://github.com/facebook/rocksdb/pull/3647

Differential Revision: D7384448

Pulled By: sagar0

fbshipit-source-id: 9b6e569f44e6df5cb7ba06413d9975df0b517d20