HID: roccat: add support for Roccat Savu

This patch adds rupport for Roccat Savu gaming mouse.

In comparison to the other Roccat modules I tried to move even more
functionality to userland.

Userland tools can soon be found at http://sourceforge.net/projects/roccat

Signed-off-by: Stefan Achatz <erazor_de@users.sourceforge.net>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>