[Download] Renaming output file of download/launch application

The download and launch application will now be named illarion.jar
instead of downloader.jar
[Client] Add background image
[Client] Add background image to additional credit screens
[Client] Re-arrange login screen buttons

It looks cleaner when the small buttons are in one row.
The login button is the most important one and should stick out, thus be on top and alone in its row.
[Client] Change button font to BlackChancery
[Client] Change login screen design

* Use caption font on labels
* Use menu font on login button
* Make credits button smaller and adjust German caption
[Client] Toggle walk/run with ctrl for keyboard and pathfinding.
[Client] Add button for toggle walk/run .
[Client] Add setting for walk as default
[Client] Follow mouse uses the run/walk toggle