Add a demo switch to enable online UI discovery

[1000i100]

For debug, UI demo and probably other stuff, it would be wonderful to have a switch in the disclaimer warning to say :

• I don't want to use it for real stuff, let me test it as is (with all spy and theft ready to stole my dummy secrets) !
  and a simple refresh will reset the switch to be sure it will never still one for real stuff.

[stewit]

Since this is still open: Some time ago I created a small fork doing something like this: https://stewit.github.io/banana_split/#/ (repo: https://github.com/stewit/banana_split)