Changes to Bot handling to allow custom Bot classes.

[ghost]

Brief overview of PR changes/additions

• Messages are no longer dressed by the portal side bot. Instead text and all relevant kwargs are passed through inputfunc through to the server side bot for handling.
  -The @irc2chan command now accepts an optional class path as an argument to use as the bot class.

Motivation for adding to Evennia

• Opening Evennia up to custom bots without having to change the Evennia folder.

Other info (issues closed, discussion etc)

[Griatch]

Merged with a rebase. Thanks for your work on this. I made some minor changes to the irc2chan command to match syntax in the rest of Evennia, but otherwise, seems to work very well!