Moved background color settings from GAL to RENDER_SETTINGS. Added RENDER_SETTINGS::TranslateColor() to convert between EDA_COLOR_T and COLOR4D.

Screen size is saved in VECTOR2I instead of VECTOR2D.

Corrected the error message about required OpenGL version for GAL. Fixed pcb_calculator .desktop file.

Removed a few RecacheAllItems() calls, some of them changed to specific type recaching (using TYPE_COLLECTOR & VIEW_ITEM::ViewUpdate() ).
Removed OPENGL_GAL::SetStrokeColor().

Changed the used framebuffer object extension from ARB_framebuffer_object to EXT_framebuffer_object (compatibility reasons).

template<> -> template <>
Some more reformatting according to uncrustify results.

Added error messages for OpenGL framebuffer errors. This should eliminate quiet segfaults in case of drivers that cannot handle multiple attachment points for framebuffers.