Small update + fixes

- updated look and feel to represent teal and orange theme (for now)
- added Healer-class
- added health-variable to Player.js
- updated main.js to check for health
- updated main.js to check for extra layers in JSON (for healers)
- updated main.js to check for collision with healers (for now in
comments)
- updated main.js with standard menu and cutscene-code
- updated main.js with checks to avoid ‘(variable) is undefined’-errors
- small update to Menu.js and Cutscene.js
- updated to do