Allow overriding cassandra-rackdc.properties location

Patch by Patrick Ziegler, reviewed by brandonwilliams for CASSANDRA-7072
Merge branch 'cassandra-2.0' into cassandra-2.1

Conflicts:
	CHANGES.txt
	src/java/org/apache/cassandra/locator/SnitchProperties.java
re-add parameter columns to tracing session

patch by dbrosius reviewed by jbellis for cassandra-6942
Merge branch 'cassandra-2.0' into cassandra-2.1
fix bad merge
Fix StorageProxy#syncWriteToBatchlog()
fix equals to compare this to the parm, rather than this to this
Preserves CQL metadata when updating table from thrift

patch by mishail; reviewed by iamaleksey & slebresne for CASSANDRA-6831
Merge branch 'cassandra-1.2' into cassandra-2.0

Conflicts:
	src/java/org/apache/cassandra/thrift/CassandraServer.java
Merge branch 'cassandra-2.0' into cassandra-2.1

Conflicts:
	CHANGES.txt
	src/java/org/apache/cassandra/config/CFMetaData.java
	test/unit/org/apache/cassandra/config/CFMetaDataTest.java