unfriend Compaction and CompactionPicker from VersionSet

Summary: as title

Test Plan: running make all check

Reviewers: sdong, yhchiang, rven, igor

Reviewed By: igor

Subscribers: dhruba, leveldb

Differential Revision: https://reviews.facebook.net/D27549
unfriend UniversalCompactionPicker,LevelCompactionPicker and FIFOCompactionPicker from VersionSet

Summary: as title

Test Plan:
make release
I will run make all check for all stacked diffs before commit

Reviewers: sdong, yhchiang, rven, igor

Reviewed By: igor

Subscribers: dhruba, leveldb

Differential Revision: https://reviews.facebook.net/D27573
rename FileLevel to LevelFilesBrief / unfriend CompactedDBImpl

Summary:
We have several different types of data structures for file information.
FileLevel is kinda of confusing since it only contains file range and
fd. Rename it to LevelFilesBrief to make it clear.
Unfriend CompactedDBImpl as a by product

Test Plan:
make release / make all
will run full test with all stacked diffs

Reviewers: sdong, yhchiang, rven, igor

Reviewed By: igor

Subscribers: dhruba, leveldb

Differential Revision: https://reviews.facebook.net/D27585
unfriend ColumnFamilyData from VersionSet

Summary: as title

Test Plan:
make release
will run full test on all stacked diffs before committing

Reviewers: sdong, yhchiang, rven, igor

Reviewed By: igor

Subscribers: dhruba, leveldb

Differential Revision: https://reviews.facebook.net/D27591
unfriend ForwardIterator from VersionSet

Summary: as title

Test Plan:
make release
will run full test on all stacked diffs

Reviewers: sdong, yhchiang, igor

Reviewed By: igor

Subscribers: dhruba, leveldb

Differential Revision: https://reviews.facebook.net/D27597
[RocksJava] - BackupInfos & Restore-/BackupableDB enhancements

Summary:
- BackupableDB deleteBackup method
- BackupableDB purgeOldBackups bugfix
- BackupInfos now available in Restorable-/BackupableDB
- Extended BackupableDBTest to cover more of the currently implemented functionality.

Test Plan:
make rocksdbjava
make jtest

Differential Revision: https://reviews.facebook.net/D27027
[RocksJava] Integrated review comments

Parameter types for BackupID are now aligned to int.
make LevelFileNumIterator and LevelFileIteratorState anonymous

Summary: No need to expose them in .h

Test Plan: make release

Reviewers: igor, yhchiang, rven, sdong

Reviewed By: sdong

Subscribers: dhruba, leveldb

Differential Revision: https://reviews.facebook.net/D27645
FlushProcess

Summary:
Abstract out FlushProcess and take it out of DBImpl.
This also includes taking DeletionState outside of DBImpl.

Currently this diff is only doing the refactoring. Future work includes:
1. Decoupling flush_process.cc, make it depend on less state
2. Write flush_process_test, which will mock out everything that FlushProcess depends on and test it in isolation

Test Plan: make check

Reviewers: rven, yhchiang, sdong, ljin

Reviewed By: ljin

Subscribers: dhruba, leveldb

Differential Revision: https://reviews.facebook.net/D27561
Merge pull request #366 from fyrz/RocksJava-Backup-Restore-Improvements

[RocksJava] - BackupInfos & Restore-/BackupableDB enhancements