add storage.cassandra.thrift.{frame_size_mb, max_message_size_mb} options
Provide default config files for TitanServer with cassandra.
Added sample berkelydb properties file for TitanServer.
Merge pull request #168 from thinkaurelius/issue_167

add storage.cassandra.thrift.{frame_size_mb, max_message_size_mb} options
merge with master