GLMixer Code

Implementation of ShaderToy GUI (Code editor with lineCount, actions of
buttons)

Continuing the implementation of ShaderToy FreeFrame plugin:
- changed functions for adding a new FFGL plugin to return pointer to
FFGLPluginSource
- Fixed mechanisms for initialization of FFGLPlugin
- fixed GUI for GLSL code editor

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