Save screenshot Viewport + Save screenshot GUI (As 2 separated options) + file name format

1. Save screenshot Viewport - no GUI from blender as btns, panels, etc.. just what we see
2. Save screenshot GUI - with GUI like now

Add some additional auto inputs template for file name format, eg:

• Blender_Screenshot_Viewport
• Blender_Screenshot_GUI

+timestamp checkbox

• Blender_Screenshot_Viewport_2021-03-23-0300
• Blender_Screenshot_GUI_2021-03-23-0301