Switch content selector to default tree-structure

[alansemenov]

Everybody loves tree-structure inside content selector in the Move dialog, so we should make this default behaviour.

NB! Since content selector can have different kinds of filtering applied to it (allowPath, allowContentType), we should make sure that we always show nodes that have children, but don't let them be selected (don't render checkbox for multi-select and don't handle the click for single-select) if they are not allowed by filters. Nodes that don't have children and are not allowed by filters should not be shown in the tree.

To enable having current "flat" structure, implement support of a config option flat:

<input name="name" type="ContentSelector">
  <label>Cited In</label>
  <occurrences minimum="0" maximum="0"/>
  <config>
      <flat>true</flat>
  </config>
</input>

[Bellfalasch]

+1 for also adding this to Image Selector, equally important to have it there too. It's almost hopeless to text-search in 1000+ item archives of images and content.

[alansemenov]

@Bellfalasch It's a bit more complicated for image selector since there we should make sure that parent nodes are not selectable and add deep filtering of nodes that don't have any image content. But we'll get there.

[Bellfalasch]

Doh, worth a shot =) At least having it added to ContentSelector is good progress. As you saw on meetup, both of these are highly requested by users. @alansemenov