emscripten compile option tweaks
Fixed emscripten stuff in AppBase.cc
Call VertexArray functions also in OpenGLES2 mode (works in emscripten)
Removed the GL_MAJOR_VERSION/GL_MINOR_VERSION display, doesn't seem to return anything meaningful on some platforms
Simplified code for determining color channels bits from pixel format
Some changes for shader compilation to make emscripten/WebGL happy
EGL display manager with emscripten support (for now)