Add ability to group attributes under specific headings in the property editor panel

[finger563]

And such headings / groups of attributes would be collapsible, and could also have an additional tooltip for the heading itself, such abilities are found for instance in Unity, where you can group class properties under headings which are automatically transformed into collapsible groups in their property editor.

[pmeijer]

I can see this being useful and after discussing with Tamas this feature could be generalized to where attribute definitions (and perhaps pointers and sets) would be able to store tags.
These could be used by ui-pieces in general (e.g. which attributes to display in a table, hidden attributes, etc.).
The down-side of this breakdown could be that for the property editor example the tags would at least have to be prefixed by group-. Not to speak of the title (for those attribute definitions themselves could have a description field added though)..

The tagging could solve component configuration based on the meta. Which in many cases has advantages compared to using component-settings or storing data in the registry of a model.