Added a new class for a list of group definitions incl. some convenience functions (mostly adding up players, groups and matches).

Introduced an operator == for comparing group definitions.

Created test cases for all non-trivial KO_Config functions.
Created a "GroupConfigWidget" and integrated it with the category tab.
Added a field for the group configuration to the database and insert some defaults upon category creation.

Added basic logic to the GroupConfigWidget. Connected the widget with the CatTab.

Added Category-functions for getting / setting the group config.