Adjustments for the fitness feature

Small adjustments in the fitness beta:
- Fix for regeneration for players in weeks with two matches, so they are not completely breathless in the second game. Regeneration is reduced, though, due to the short week
- Fix for substituting players when not watching their own match
- Fix for endurance, it is now clamped to a maximum amount of 100
- Fix for transfer offer notification in diary, it won't get repeated for countless weeks anymore
- Reduced size of savegames massively, in an extreme case from 200 MB down to 9 MB