Add option to activate a static when a pattern is active

[matsn0w]

Is your feature request related to a problem? Please describe.
It would be nice if it was possible to activate an extra as a static when a pattern is active. This can be useful if an extra should be 'turned on' for the entire loop.

Describe the solution you'd like
Need to think this through carefully. Should be scalable and easy to implement in both the Configurator and the XML.

Describe alternatives you've considered
Currently, a work-around is enabling the extra in each step, but this has the downside of flashing at the end of each loop.

Additional context
This issue was raised by a guy who is trying to create a vehicle with a control panel for the lights (having an visual indicator showing whether the lights are turned on or not).