[form-builder] Fix bug with fieldsets

[bjoerge]

Something got messed up with the defaults here, so fieldsets ended up being non-collapsible and collapsed by default, which was unfortunate. This fixed it so that the defaults are:

collapsible: true
collapsed: true

[kristofferjs]

The default should be collapsible: false.
Fieldsets should be non-collapsible as default (and not collapsed).

[bjoerge]

Ah, aight. We should probably change that default in next, then.

[kristofferjs]

If i remember coreectly: We set the collapsed based on the level in form-builder. So if there are many nested fieldsets, they will auto-collapse on level > 2 if they are collapsible.

[bjoerge]

So there are several cases to consider here:

1. {collapsed: true} - this should force the fieldset to be collapsible, so this would resolve to {collapsed: true, collapsible: true}
2. {collapsible: true} - resolve to {collapsible: true, collapsed: false}
3. {collapsible: false, collapsed: true} - what to do? The field will be hidden and not possible to expand at all. I feel the most sane would be to handle it as {collapsible: true, collapsed: true}
4. {collapsible: false, collapsed: false} - as is.
5. {collapsible: true, collapsed: true} - as is.

How should these apply on level > 2?

[kristofferjs]

I think it is best only to handle collapsible if it is true. Ignore collapsed if collapsible is false/undefined.

[kristofferjs]

Level > 2 should be {collapsible: true, collapsed: true} as default. (if we set the levels here)