Write more exemplary example scripts and unit tests

[kckrinke]

• existing ones are semi-broken due to the callback demo
• not all features demonstrated, goes along with matching unit tests

[kckrinke]

Generally speaking, the unit tests are much more thorough and actually useful. Still in flux to a degree but the pattern is formalized.

Specifically need to implement XOSD, Nautilus, Druid and Menu test_mode support.