Make it possible to compile Analitza without OpenGL

Since some time ago, Analitza master required OpenGL for building
Analitza completely. This commit makes OpenGL a conditional dependency
and some parts of AnalitzaPlot will be left out if OpenGL is not found,
more specifically plotsview3d.cpp and plotter3d.cpp.

BUG: 310720
CCMAIL: percy.camilo.ta@gmail.com