Added timer and level in a own view

ScreenHeader is a .js file containing 2 views:
- LevelHeader
- TimerHeader
Removed the drawing of timer and level from
the screen.js class.
Changes the css to style the new elements.
Added text for timer and level in index.html.
Added the views to the app.js file.
Merge branch 'master' of https://github.com/kpro-gr10/Power-Supply

Conflicts:
	www/css/app.css