Stop treating filtered messages as errors

Each channel has a config for asynchronous messages that can filter what will
be sent to the controller. Filtered message is not an error.
Add controller's scenarios for starting equal and slave controllers

The two scenarios equal_controller and slave_controller help to reproduce
the environment for isse #97.
Make running the OF controller easier

Now the of_controller_v4.sh script has a few options facilitating its usage:
-d that turns on the debug mode
-p <port_number> that makes the controller to listen on a specified port
-s <scenario> that makes the controller to run the specified scenario after a
connection to a swtich is established; if the scenario is not defined in
the controller the "all_messages" scenario will be run by default
Merge pull request #123 from FlowForwarding/issue97

Not treat filtered messages as erros; add scenarios for #97; improve using the controller