Remove signed functions from common.glsl

The longs are packed with the sign encoded in the MSB so there is no
need for it anymore
Add the fragment shader files to the project

Don't know why the haven't been there before
I just started since a long time. Just commit everything open first.
Minor change to use defined constant
Fix printSignedLabels function
Fixed the blending stage. Finally addition is done properly
Finish the statsPhase so far. Works on desktop

TODO: test on pi