Code style fixes:
* use camelCase
* don't use yoda conditions
* Add back working screen initialization code.
* Remove commented code
Move rendering API to RenderDevice file
Fix Linux build
Make icons extern Renderable.
Add copy constructor/destructor/operator= to Renderable class. Add setters and getters
Fix power tree background image loading
Merge remote-tracking branch 'remotes/upstream/master' into render_refactor
Fix build
Fix gcc build and rendering of map tiles

Object renderables like the Avatar and NPCs are still broken though.
Fix Animation::getCurrentFrame()

There's still the issue of returning a reference to a local variable.
Perhaps adding a dummy Renderable to the Animation class would take care
of that?