Fixes access violation if colorbrewer,json could not correctly be opened for ColorSchemePresetsWidget initialisation, ref #25.
Adds method to ensure a default selection of a ColorScheme in ColorSchemePresetWidget, ref #25.
adjust cmake and refine color preset fix
Fix git revision extraction
Fix compilation for Linux
Merge branch 'master' into color_gradient

Conflicts:
	source/glwhite/CMakeLists.txt
	source/tests/glwhite-test/CMakeLists.txt