Remove Trigger class and migrate collision code to Behavior
First iteration of level loading: freezes to load the next level as you touch a door
Load next level in background; start rendering new level while animating door before we switch to new level. Runs smoothly in OpenGL but for some reason SDL has horrible performance during the first call to draw().
Implement context loss and restore functions for OpenGLCanvas
added sdl 2 support: it builds but doesn't yet run