Log improvements.

Unfortunately, a world of consistent log entries doesn't exist. Here's what
changed:

* Add abstract getHistoryType() to AbstractFormatter - used to automatically
  find specific history i18n messages (like already done for -irc)
* Since we're now doing the above on a more generic level, irc-specific code
  is removed
* Changed link to board to "<link to thread> on <link to board>" in RC & CU
* Added "<link to thread> on <link to board>" in Contribs
* Added some new near-empty messages for RC & Contribs
* Removed tempHackyChanges (to be replaced by these permanent,
  non-hacky-but-still-high-maintenance-and-error-prone changes)

Change-Id: Icf9715f7b0e5bf69f5044a5475c5067f7d419457
Merge "Log improvements."