Add reward on successful action

[breznak]

on correctly passing an obstacle, after several minutes of driving, on passing a cognitively demanding situation... give a reward (play a song, green screen with trophy icon, ...) Make this an optional functionality, so the impact can be validated

Subtask of #24

[breznak]

OK, here's an updated plan:

• [ ] implement means to show/act on reward:
  • [x] show text/image (e.g :+1: ) on screen ... https://github.com/breznak/openDS/issues/32#issuecomment-253496420
  • [x] play a sound: cz.cvut.utils.PlaySound(String pathToFile)
  • [ ] change screen color/flash/blink cz.cvut.utils.Utils.changeScreenColor(Color c, int timeoutMs, bool smooth) // static method, extract from DarkeningDistraction
• [ ] refactor DisctractionClass
  • [x] merge in it functionality of ListOfDistractions
  • [ ] abstract void showReward() //can also do nothing
  • [x] require int reward in constructor
  • update global reward on collection
  • [ ] "automatically" detect when/if reward is collected, write to log
  • [ ] remove DistractionSettings, hold the info in DistractionClass.settings hashmap