File cleanup

[jorgenschaefer]

There's a lot of cruft in the files by now. Could do with some cleanup.

Some ideas (rethink first, this is not final):

• Incorporate lui-format.el into some other file, e.g. lui.el
• Merge lui-irc-colors.el into circe.el. It's loaded by default nowadays.
• Rename lui-logging.el to circe-logging.el and lui-autopaste.el to circe-autopaste.el
  • If we do this, we should leave a file under the original name that tells the user about it when loaded, for one or two versions.