Implemented a better "Can-We-Add-Players-To-Categories" function in the lib.

Enabled assignment of categories to newly created players in the GUI.

Fixed a bug that prevented proper name changes of players in the GUI.
Added GUI-functionality to assign and remove player to/from categories
Extended the PlayerTableModel to show the category-assignment in a dedicated column
Added GUI-functionality to change a player's team assignment
Huge commit, introducing:

  * A new tab for category settings

  * Lib logic for setting special category parameters

  * GUI and lib logic for setting "Draw yes/no" and score for winner / draw
Implemented basic support for creating and splitting player pairs