Refactoring : rename GLC_StructOccurence to GLC_StructOccurrence
Add some unfinished modifications to selection functionnalities
Refactoring
SelectionEvent usage.
Add the possibility to construct orthonormalMatrix or frustumMatrix from
GLC_Matrix4x4 class
Add the possibility to use GLC_Viewport class to do some calculus
without OpenGL calls
Activate Space partitionning in the second view