Block internal_stats in ROCKSDB_LITE

Summary: Block internal_stats in ROCKSDB_LITE.

Test Plan: make OPT=-DROCKSDB_LITE shared_lib

Reviewers: ljin, igor

Reviewed By: igor

Subscribers: dhruba, leveldb

Differential Revision: https://reviews.facebook.net/D29541
RocksJava - FindBugs issues

Addressed some FindBugs issues.
[RocksJava] Remove obsolete dbFolder cleanup
[RocksJava] Comparator tests for CF

- Added AbstractComparatorTest.
- Fixed a bug in the JNI Part about Java comparators
[RocksJava] Minor test improvements

Some minor test coverage improvements.