There were no filters for action displaying. All actions were active from the start, even if they are not possible.
I added action filter that will remove impossible actions:
- COMPLETE_MAX and MULTIPLE_PANEL for non-repeatable challenge,
- already completely finished challenge.
Fixes#307
Add a new method that updates unlocked level list without changing active level. This method returns if last unlocked level was changed, and in that case it triggers whole gui rebuilding.
