Figure out what to do with control field names
The amount of control fields (that are always present in modules) keeps growing which limits the field names available. Introducing the underscore in the _stp field was an attempt to make them unique enough to not collide with "normal" field names people may want.
The problem there however is that it currently can't be used in the templates format class as that uses underscores to indicate marker types (e.g. _if). This can of course be changed but that would mean all templates require adjusting... tho that'll probably be already necessary when changing show_count to something like _show_count.
Current list of control fields:
- Data control: "m", "a", "e", "r"
- Show results: "show_from", "show_count", "show_total", "show_page", "show_pages"
- Aggregation: "aggregation_field", "aggregation_type", "aggregation_method", "aggregation_interval"
- Search: "search", "searchFields"
- Database info: "info_type", "info_rows", "info_insertID", "info_created", "info_updated"
- Other: "_stp", "reload_trigger", "treedepth"
- Default fields: "nr", "catnr", "owner", "added", "updated", "deleted"
