Include high level sstables in lower level compactions if not compacted for a while.

Patch by marcuse, reviewed by kohlisankalp and yukim for CASSANDRA-7414
Merge branch 'cassandra-2.0' into cassandra-2.1

Conflicts:
	src/java/org/apache/cassandra/db/compaction/LeveledManifest.java
Merge branch 'cassandra-2.1' into trunk
Merge commit failure policy into 2.1

patch by Benedict Elliott Smith; reviewed by Marcus Eriksson for CASSANDRA-7429
Merge branch 'cassandra-2.1.0' into cassandra-2.1
Merge branch 'cassandra-2.1' into trunk
Optimise CellName/Composite comparisons for NativeCell

patch by Jake Luciani and Benedict Elliott Smith for CASSANDRA-6755
Merge branch 'cassandra-2.1' into trunk
fix CHANGES.txt
Merge CHANGES.txt from 2.1.0
fix CHANGES.txt
Merge branch 'cassandra-2.1' into trunk
Fix Assertion errors when using empty clustering with static columns

patch by slebresne; reviewed by iamaleksey for CASSANDRA-7455
Merge branch 'cassandra-2.0' into cassandra-2.1.0

Conflicts:
	CHANGES.txt
	src/java/org/apache/cassandra/db/compaction/LeveledManifest.java
Merge branch 'cassandra-2.1.0' into cassandra-2.1

Conflicts:
	CHANGES.txt
	src/java/org/apache/cassandra/db/compaction/LeveledManifest.java
Merge branch 'cassandra-2.1' into trunk
Merge branch 'cassandra-2.0' into cassandra-2.1.0

Conflicts:
	src/java/org/apache/cassandra/cql3/statements/ColumnGroupMap.java
Merge branch 'cassandra-2.1.0' into cassandra-2.1
Merge branch 'cassandra-2.1' into trunk
typo