Enhance labels

[ReViCo-be]

Labels are currently a single item, it would be useful if we could use set extra informatie for the labels, f.ex.:

• Have a label "label A" which can have multiple child labels, resulting in "Label A: Child 1", "Label A: Child 2"... (the value is then selected when selecting the label).
• Have the labels defined on a domain level, this allows a lower level domain to create it's own labels for his domain.