Add checking consumer count on multiple rabbitmq queues

Allows passing in a comma separated list of queue names to check
Returns the names of queues in critical/warn state as well as any missing queues
Renames the class so the correct name is returned in errors (CheckRabbitMQConsumers  vs CheckRabbitMQMessages)
Add myself on the copyright

Note:  I realize that a very similar change was made in https://github.com/sensu/sensu-community-plugins/pull/875 early this morning.  This change still returns missing queues and returns the names of queues in a failing state which is important for quick issue resolution.