Improve check probability calculation

[Bernhard Jung]

1. Allow to see the probability for checks with a modificator.
2. Allow to easily set common modifications like encumbrance.
3. Include other abilities that modify the chance like aptitude.

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[Nando Neck]

when you also add something like the specialabilities like “kunstbegabt“ for example this would require a lot more programming effort, because you would need to configure for all thos spabs some custom parameters to modify QS FP and whatsoevery

same goes also for some advantages, like “wolfsblut“ …