Finally merging in libtomahawk changes from GSoC

[Dominik Schmidt]

Hey Lucas,

as it seems you're still very busy, I decided to rebase master onto your 
branch myself, so we can pull in your stuff and stabilize it in master.

Doing this I had to edit your commits here and there and thought it 
would be a good idea to ask for your permission to merge them like they 
are now..

FYI, I removed two commits:
* the FindLibattica change
   that seemed to be rather a workaround than a fix
* the commit generalizing the authorization request handling
   we refactored the whole sip system lately and this was more or
   less unmergeable


You can see the pull request at

https://github.com/tomahawk-player/tomahawk/pull/152


Please let me know as soon as possible if you're ok with it.


Best regards,
Dominik