Prepared for perks upgrade mechanism

Prepared the system for perks upgrades:
- added a training node to the global config to set the costs (currently
not working, throws NRE when loaded)
- added UpgradeCost structure
- added dictionary of training costs to DangIt
- huge rewrite of the roster window: the code has been splitted in
subfunctions to keep things clean, fixed bug that caused the selection
to go out of bounds when changing filters. Also changed the overall
layout.