First steps toward rewriting shortcuts_greeder

Added some more user-friendly settings page
Cleaned the list of shortcuts and the way it works

TODO :
* Check everything is ok
* Implement shift, ctrl etc.
* Prevent user to link the same key to two different shortcuts
Following refactoring

Added possibility to have shift+key or ctrl+key for a shortcut
Prevents same key for two different shortcuts
...

TODO : Test everything is ok
Bug correction

Corrected some bugs affecting shortcuts.
Shift/Ctrl + key may not work properly, working on it.
Shortcuts_greeder refactorization finished

Now there's a user friendly interface to change shortcuts
You can now use Ctrl+key or shift+key as a shortcut
Duplicated shortcuts were cleared

Should work now, as far as I tested. Please report any issue.