Summary:
RocksDBOptionsParser now supports CompressionType and the following
pointer-typed options in RocksDBOptionParser
for sanity check:
  prefix_extractor
  table_factory
  comparator
  compaction_filter
  compaction_filter_factory
  merge_operator
  memtable_factory

In the RocksDB Options file, only high level information about pointer-typed
options are serialized, and those information is only used for verification
/ sanity check purpose.

Test Plan: added more tests in options_test

Reviewers: igor, IslamAbdelRahman, sdong, anthony

Reviewed By: sdong

Subscribers: dhruba, leveldb

Differential Revision: https://reviews.facebook.net/D47925