Comment 0 for bug 1953355

The GUI should disable that a variable called e.g. x appears inside of some
enumeration type as its element, e.g. A is {x,y,z}. The check should be added
both when a new variable is created and when a new color is added to an enumeration
colortype.

Also, two different enumeration types should be disjoing, so e.g. the following
should be disallowed:

A is { c, d, e}
B is { e, f, g}