Optimize single partition batch statements

patch by slebresne; reviewed by benedict for CASSANDRA-6737
Merge branch 'cassandra-2.0' into cassandra-2.1

Conflicts:
	src/java/org/apache/cassandra/cql3/statements/BatchStatement.java
	src/java/org/apache/cassandra/cql3/statements/DeleteStatement.java
	src/java/org/apache/cassandra/cql3/statements/ModificationStatement.java
	src/java/org/apache/cassandra/cql3/statements/UpdateStatement.java
	src/java/org/apache/cassandra/db/Mutation.java
Merge branch 'cassandra-2.1' into trunk
Disallow post-query re-ordering when paging

patch by slebresne; reviewed by iamaleksey for CASSANDRA-6722
Merge branch 'cassandra-2.0' into cassandra-2.1

Conflicts:
	src/java/org/apache/cassandra/cql3/statements/SelectStatement.java
Merge branch 'cassandra-2.1' into trunk
Completer shall always return a collection
Merge branch 'cassandra-1.2' into cassandra-2.0
Merge branch 'cassandra-2.0' into cassandra-2.1
Merge branch 'cassandra-2.1' into trunk
fix CME in SessionInfo updateProgress affecting netstats
patch by Josh McKenzie; reviewed by Tyler Hobbs for CASSANDRA-6577
Merge branch 'cassandra-2.0' into cassandra-2.1
Merge branch 'cassandra-2.1' into trunk
Fix overflow of memtable_total_space_in_mb
patch by Benedict Elliott Smith; reviewed by jbellis for CASSANDRA-6753
Merge branch 'cassandra-2.1' into trunk
Fix assertion error in ALTER TYPE RENAME

patch by mstepura & slebresn; reviewed by mstepura & slebresne for CASSANDRA-6705
Merge branch 'cassandra-2.1' into trunk
Scrub should not always clear out repaired status.

Patch by marcuse, reviewed by jbellis for CASSANDRA-5351
Merge branch 'cassandra-2.1' into trunk
correct more uses of isMinimum (CASSANDRA-6734)