cqlsh DESC CLUSTER fails retrieving ring information

patch by Adam Holmberg; reviewed by mstepura for CASSANDRA-7687
Merge branch 'cassandra-2.1.0' into cassandra-2.1
Merge branch 'cassandra-2.1' into trunk
Adding new Compaction Strategy

- Based off LeveledCompaction, but allows for levels to be overlapping
  at a level higher than 0
- When an overlapping compaction has occurred, and no other compactions
  are necessary, OCS will work on de-overlapping the levels
- A new tool has been added to nodetool, 'getmanifest', which allows for
  the inspection of where in the levels the SSTables currently are