add demo.ino as state to adem.ino

[lebeno]

The demo mode is currently a separate project. It should better reside in a separate demo folder as required by the Arduino IDE.

We want to integrate the demo.ino code into the adem.ino project as a separate state that can be started from the setup page shown in the AP mode of the ADEM project.

[lebeno]

moved demo.ino to subfolder demo in commit fd995e8