Update sstablesPerReadHistogram to use biased sampling
patch by jbellis; reviewed by yukim for CASSANDRA-6164
add live/tombstoned histogram counts to cfstats
patch by Mikhail Stepura; reviewed by jbellis for CASSANDRA-5889
merge from 1.2
add 6164 to NEWS
merge from 2.0
rewrite sendRR API to fix regressions from #6132
patch by jbellis; reviewed by brandonwilliams for CASSANDRA-6165
Fix NPE if StorageService.getOperationMode() is executed before full startup
patch by cwarrington reviewed by dbrosius for cassandra-6166
Log UnknownColumnfamilyException when closing socket
patch by Suresh; reviewed by Sergio Bossa and jbellis for CASSANDRA-5725
merge from 1.2
update Thrift server comment
Properly error out on CREATE INDEX on counter tables

patch by slebresne; reviewed by jbellis for CASSANDRA-6160
Merge branch 'cassandra-1.2' into cassandra-2.0

Conflicts:
	src/java/org/apache/cassandra/cql3/statements/CreateIndexStatement.java
Handle JMX notification failure for repair

patch by yukim; reviewed by pcmanus for CASSANDRA-6097
Merge branch 'cassandra-1.2' into cassandra-2.0

Conflicts:
	src/java/org/apache/cassandra/tools/NodeProbe.java
fix trace activity from #6133
Merge branch 'cassandra-1.2' into cassandra-2.0
Fetch no more than 128 splits in parallel
patch by Patricio Echague; reviewed by jbellis for CASSANDRA-6169
Merge branch 'cassandra-1.2' into cassandra-2.0
cleanup
remove decompression code in CompressedSequentialWriter
patch by dbrosius reviewed by jbellis for cassandra-6176