Correctly handle null in conditions with TTL

patch by slebresne; reviewed by iamaleksey for CASSANDRA-6623
Account for range and row tombstones in tombstone drop time histogram.

Patch by marcuse, reviewed by jbellis for CASSANDRA-6522
Expose bulk loading progress over JMX
patch by Tyler Hobbs; reviewed by Nick Bailey for CASSANDRA-4757
Improve nodetool cfhistograms formatting
patch by Tyler Hobbs; reviewed by Benedict Elliott Smith for CASSANDRA-6360
Fix upgradesstables NPE for non-CF-based indexes
patch by Sergio Bossa; reviewed by jbellis for CASSANDRA-6645
Fix upgradesstables NPE for non-CF-based indexes
patch by Sergio Bossa; reviewed by jbellis for CASSANDRA-6645
merge from 1.2
Merge remote-tracking branch 'origin/cassandra-2.0' into cassandra-2.0
Update CHANGES for CASSANDRA-6522
nope 6522 was not merged from 1.2
Add nodetool taketoken to relocate vnodes.
Patch by brandonwilliams reviewed by jbellis for CASSANDRA-4445
Failure detector correctly converts initial value to nanos
Patch by brandonwilliams reviewed by jbellis for CASSANDRA-6658
remove dead code
Fix unwanted schema pull while upgrading nodes from 1.2 to 2.0
Patch by Sergio Bossa, reviewed by brandonwilliams for CASSANDRA-6678
Merge branch 'cassandra-1.2' into cassandra-2.0
Fix unwanted schema pull while upgrading nodes from 1.2 to 2.0
Patch by Sergio Bossa, reviewed by brandonwilliams for CASSANDRA-6678
Log heap pool sizes at startup.
Patch by brandonwilliams, reviewed by Lyuben Todorov for CASSANDRA-6657
Fix mean cells and mean row size per sstable calculations
patch by Paulo Gaspar, jbellis, and Marcus Eriksson for CASSANDRA-6667
Merge branch 'cassandra-1.2' into cassandra-2.0
Compact hints after partial replay to clean out tombstones
patch by jbellis; reviewed by ayeschenko for CASSANDRA-6666