Distorted Android

One more APP converted. Only 2 remain.

Major:

1) in the Library, fix the fact that some applications (those that were creating their DistortedSurface objects outside of onSurfaceCreated or onSurfaceChanged) would not render after the activity went to background (press POWER to see that).
2) in the Apps, call the new 'Distorted.onPause()' API to fix the above problem...

It now automatically chooses OpenGL ES 2.0 and GLSL 100 or OpenGL ES 3.0 and GLSL 300.

Postprocessing effects will not work on OpenGL ES 2.0 contexts.

New 'glClearColor' and 'glClearDepthf' APIs in OutputSurface. This fixes the 'transparency' regressions from last commit.

Minor

1) stop culling back face
2) reset OpenGL state beore each render (and not in onCreate)
3) Improve Matrix3D so that we can test negative Scales

Change the the render() API!

THis introduces some regressions with the Effects3D app.

Major: change of API.

Split DFramebuffer into Framebuffer and Screen; introduce the 'DistortedInputSurface' and 'DistortedOutputSurface' interfaces.

Try using OpenGL ES 3.0 everywhere (but if device does not support it, try creating 2.0 context - this is important because of the emulator!)

rename all the 'grid' variables to 'mesh'.