Reorder questions/items

[losolio]

As a form designer I could reorder questions/items so that I could make a good sequence of questions in the form.

Preferably it should both be possible to change the sequence and keeping the parent, but it should also be possible to change the level of item, or move the item to another group.

This will introduce the possibility for the form designer to make invalid form definitions, and we will need some form of validation warnings when the tree structure is invalid.

• [x] Questionnaire table of contents
• [x] Reorder sequence within a parent
• [x] Change parent of item
• [ ] Consider showing message if invalid sequence or structure, ie enablwhen condition answer is later in form