(MCO-360) Remove all references to the 'mcollective' agent

Controller messages have been deprecated for an extremely long time.
After deprecating it we stopped processing messages directed at the
'mcollective' agent but we are still connecting to its related queues
and topics.

This commit removes all trace of the 'mcollective' agent and controller
messages.
Merge pull request #204 from ploubser/mco-360

(MCO-360) Remove all references to the 'mcollective' agent
(MCO-199) Fix halt_code to return the correct exitcode for mco ping

When calling halt_code with the client object created from a mco ping
application we are in the special case where we have 0 nodes discovered
and a non zero amount of responses.

This commit changes the list of "return if" statements in favor of a
if/else statement and adds the check where discovered = 0 but responses
> 0, allowing the method to behave as documented and ping to work as
> intended.
Merge pull request #205 from ploubser/mco-199

(MCO-199) Fix halt_code to return the correct exitcode for mco ping
(MCO-407) Add requirement for connector plugins to have ddl files.

Due to the primary connector plugins being mainly shipped with core and
developed by Puppet Labs fixing bugs or extending the connectors often
require changes in core to happen at the same time. This puts us in the
position where connector plugins often depend on specific minimum
version of MCollective but that we cannot enforce.

This commit adds the requirement that connector plugins should always
ship with a ddl.

(MCO-406) Add DDL's to Connectors

This commit adds ddl's to both the ActiveMQ and RabbitMQ connectors and
adds test coverage to the MCollective::Connector::Base class.
Merge pull request #206 from ploubser/mco-407

(MCO-406) and (MCO-407)
(MCO-410) Fix direct addressing

MCO-360 broke direct addressing by inadvertently removing the method
call that created the subscription to the mcollective.nodes queue.

This commit replaces that call but also clarifies the intent by adding
comments and wrapping it in a new method call which has been appropriately
named.
Merge pull request #207 from ploubser/mco-410

(MCO-410) Fix direct addressing