Change license to GPL v3

It's because PyQt. The core functions will stay under the zlib license.
Fix merging error
Code refactoring and bugfixing
Add Crea path functionality
Some bugfixing
Separation done

core is licensed under the zlib license.
The whole project is licensed under the GPL v3 license.
Update project file
Make licensing more clear
Make licensing stuff clearer

Now it shoud be absolutely clear how the licenses work.
Merge for merging sake
Merge branch 'desophos-master'
Doesn't work right. Doesn't matter.

I'll rewrite most of the code
Merge branch 'desophos-save-modlist'