Extend limits.conf in debian packaging.

Patch by brandonwilliams for CASSANDRA-6104
Add UNLOGGED, COUNTER options to BATCH docs

patch by Tyler Hobbs; reviewed by Sylvain Lebresne for CASSANDRA-6816
comment CqlRow for #6807
nodetool status should issue a warning when no keyspace is specified
patch by Vijay; reviewed by Brandon Williams for CASSANDRA-6168
status output is confused when hostname resolution is enabled
patch by Vijay; reviewed by Brandon Williams for CASSANDRA-6896
Fix SSTable not released if stream fails before it starts

patch by yukim; reviewed by Richard Low for CASSANDRA-6818
Fix typo in DeletionInfo
Update versions and NEWS for 1.2.16 release
Fix batchlogManager#deleteBatch() use of millisecond timsestamps

patch by Aleksey Yeschenko; reviewed by Pavel Yaskevich for
CASSANDRA-6822