fix #35 add and bind action for global shader update (works)
Merge pull request #36 from cgcostume/global_shader_update_35

fix #35 add and bind action for global shader update (works)
Merge branch 'master' into basic_screenshot_module_12

Conflicts:
	libs/gui/viewer.cpp
	libs/gui/viewer.h
	libs/gui/viewer.ui