Support for variable groups with differing numbers of outcomes

[nathanielvirgo]

This is an enhancement request.

For some use cases it will not make sense to organise the variables into groups. The logical thing to do in such a case would be to put all the variables into a single group and just add that to the graph. However, this isn't currently possible if the variables don't all have the same number of outcomes.

As a workaround, I'm currently putting each variable in a NDVariableArray with a single element, but that leads to a lot of unnecessary syntax, since I have to refer to each variable as ("MyVariableName", 0) instead of "MyVariableName".

Hence I would like to request a variant on VariableDict in which each variable can have its own number of outcomes. This would be very useful for cases like this.