Update ParserLevel : can specify a background music for a level.
Details :
- custom property concerned : BackgroundMusic
- 2 sound files added in assets/audio/backgroundMusic
- update SoundEntity : has a reference to the sound instead of an index of the sound in the array of sounds in SoundManager
Add sounds for all existing levels.
fix #130
Details :
- zone 1 : lvl_Sneeze.ogg
- zone 2 : lvl_Fever.ogg
- zone 3 : lvl_Headache.ogg
- by default if nothing is specified : Symptogen.ogg
Merge branch 'develop' of https://github.com/Symptogen/Symptogen into develop