Document GUI

[ftomassetti]

Importing the issue from Mindwerks/worldengine#42

Fill the README (Screenshots!) and in the wiki

https://www.youtube.com/watch?v=uc4Dwo6aBgE
^-- just need a placeholder for when we re-do the GUI :)

[psi29a]

Thanks for posting that video... gives me "ideas". :D

[ftomassetti]

I just copied it from the issue in worldengine, where you posted it :)