Remove useless Logger includes sprinkled all over the place.
Remove a bunch of things from Buteo log handling.

- File logging: this wasn't "proper", as it didn't handle rotation etc, having
  the potential to fill the user's disk. Furthermore, the journal can persist log
  contents anyway.
- Log formatting: QT_MESSAGE_PATTERN can replace this.
- Indentation: Nothing was actually using this.

Furthermore, the actual logging is now handled by whatever the installed message
handler was: i.e. buteo does not try make decisions about what to do except
performing some general filtering.
Remove __FILE__ and __LINE__ from Buteo debug.

QT_MESSAGE_PATTERN can do this for us, universally.