GLMixer Code

Added details for OSX compilation

Complement information for OSX system; recognize .glm files associated to GLMixer

Fixed horizontal mirror.

Added reference to parent source to FFGL plugins. New field for parent source in ShaderToy editor.

Slight improvements of GUI (margins, icons size, etc.) for OSX.

Add Custom QApplication to handle OSX file openning events.

Improving visual appearance of GUI under OSX.

BugFix; initialization of noise for Algo Source.

Cleanup Algorithm source and added two new patterns (hue color). Some
performance improvement.

Bug Fix : avoid crash on failed session load.