Desktop mode compatibility

[jvolker]

Implements: #11

TODO:

• Currently fails with "Package glfw3 was not found in the pkg-config search path." On Pi 4B with Raspian OS.
  Might be related to: Compilation fails on Pi 4 B patriciogonzalezvivo/glslViewer#179
• keep console mode compatibility

[coveralls]

Coverage remained the same at 100.0% when pulling 17740b3 on jvolker:feature/desktop into 745b819 on OpenframeProject:master.