Forbid re-adding dropped counter columns

patch by Aleksey Yeschenko; reviewed by Jonathan Ellis for
CASSANDRA-7831
Merge branch 'cassandra-2.0' into cassandra-2.1.0

Conflicts:
	CHANGES.txt
Merge branch 'cassandra-2.1.0' into cassandra-2.1
Merge branch 'cassandra-2.1' into trunk
Update version number for 2.1.0-rc7
Better err msg when condition is set on PK column

Patch by Tyler Hobbs; review by Sylvain Lebresne for CASSANDRA-7804
Merge branch 'cassandra-2.0' into cassandra-2.1.0
Merge branch 'cassandra-2.0' into cassandra-2.1

Conflicts:
	CHANGES.txt
	src/java/org/apache/cassandra/cql3/statements/ModificationStatement.java
Merge branch 'cassandra-2.1.0' into cassandra-2.1
Merge branch 'cassandra-2.1' into trunk
Ninja: fix bad merge of CASSANDRA-7804
Merge branch 'cassandra-2.1' into trunk
don't mask fields (BatchStatement.type v. Message.type)
don't declare throwing exceptions that aren't
minor javadoc fixes
Track added sstable size correctly

Patch by marcuse; reviewed by jbellis for CASSANDRA-7239
Merge branch 'cassandra-2.1.0' into cassandra-2.1

Conflicts:
	CHANGES.txt
Merge branch 'cassandra-2.1' into trunk
Don't allow marking already compacted sstables as compacting.

Patch by marcuse; reviewed by yukim for CASSANDRA-7145
Merge branch 'cassandra-1.2' into cassandra-2.0

Conflicts:
	CHANGES.txt