Unclear meaning of traffic sign - variability

[HendrikAmelunxen]

Describe the bug

The meaning of "variability" in the traffic sign is not clear.
The first description states that it should be used for objects which might change in position (for example temporary traffic signs in construction areas):

The description in the enum states that it should be used for traffic signs which content might change (for example electronic traffic signs on a sign bridge):

The meaning of the variability property should be clarified.

[jdsika]

Discussion:

1. Create a pull-request changing the description to make the current meaning clearer.
   Idea: "This value indicates if a sign is dynamic regarding its content e.g. electronic speed limit sign and/or regarding its position on the road"
2. Change headline of this ticket/or create new one to discuss potentially separating the attributes of changing the POSITION of a sign and the CONTENT.

The example we have to keep in mind:
A pickup truck at the Autobahn that carries a sign for a construction site which moves on the car, may be blinking and is enforceable regarding traffic rules.

[thempen]

The unclarity was merged. #671