Fixes #21 - ended up going a different route with this one.

Adds methods to Plugin Manager to inspect the plugin config to see if
the plugin has a configured channels option.

This new config option allows something like this:

"channels": {
	"whitelist": [
        	"#burrito"
         ],
         "blacklist": [
                "#guacamole"
         ]
}

Now the bot will ignore #guacamole but continue to send titles elsewhere. Currently only affects
the Titler plugin.