Adding basic plugin manager.
err should be null if there are no errors
Plugin unloading is now functional
Let's listen for commands properly.
Refactoring some of this, it's pointless to make sure the function is a function since we'll pooling from a set list.
Fixing unloading and exceptions
If we have an error, return it.
Merge branch 'feature-plugin-manager' of github.com:Modubot/Modubot.js into develop