Support pluggable internode authentication

patch by Aleksey Yeschenko; reviewed by Brandon Williams for
CASSANDRA-5401
Merge branch 'cassandra-1.1' into cassandra-1.2

Conflicts:
	CHANGES.txt
	NEWS.txt
	conf/cassandra.yaml
	src/java/org/apache/cassandra/config/DatabaseDescriptor.java
Merge branch 'cassandra-1.2' into trunk

Conflicts:
	src/java/org/apache/cassandra/config/DatabaseDescriptor.java
add nodetool statusbinary command
Merge branch 'cassandra-1.2' into trunk