WIP retrofit new MonoGame based engine

Replaced GameFramework structure
Imported MonoGame engine implementation

Add linked to other base launcher projects
Retrofitted the old sample game

Sandbox for testing
Added license
Removed old projects
Removed more obsolete files
Added the ShootEmUp sample
Removed to old ShootEmUp sample
Refact Sandbox sample

Added HubScreen (still WIP)
Updated HubScreen

For Sandbox and ShootEmUp samples
MonoGameBase now use ScreenNavigation class