Update Priam for Cassandra 1.2 support.

Added support for Cassandra 1.2 features like MurmurPartitioner, cassandra.replace_address_first_boot, cassandra.yaml additions.  Like the Netflix fork this does not support vnodes--# tokens must be 1.

Ported over a number of changes from the Netflix trunk.

Specialized the code to Bazaarvoice's use of Priam.  Especially, removed all code related to backup since we use a different set of scripts for backup.  Over time the Bazaarvoice fork of the backup code was not maintained and was very likely broken.  It seemed best to remove the broken code rather than keep it and cause confusion down the road.

The maven artifacts were reorganized to match the Netflix trunk.  In particular, the "core" directory was renamed to "priam" and the code added to the Cassandra classpath was moved into the "priam-cass-extensions" artifact, to be installed using "-javaagent:<jar>".  Because of this it's probably easier to review this pull request by creating separate directories for the old & new code and using diff tools to compare the directories.

Now requires JDK 1.7+.
Agree, I don't think it's possible for wrap around to actually happen w/16 byte tokens, but I've fixed the code just in case.