GLMixer Code

Working implementation of Shadertoy plugin with Freeframe 1.6 under
Linux. Still a lot to do :
GLSL code editor is buggy
Properties not synched
Code is not saved

Implementation of Shadertoy plugin with Freeframe mechanisms
- changed files for compilation of FFGLPluginInstance
- added DLL communication for code get and set

On-going implementation of opengl plugin with Shadertoy and Freeframe

Draft implementation of FreeFrameFragmentCodePlugin

Draft implementation of GUI for GLSL Fragment Code plugin

Draft implementation of GLSL Editor

Fix graphical issues with textures