* Initial work on #13283
* Enable passing TomSelect HTML template attibutes on DynamicModelChoiceField
* Merge disabled_indicator into option_attrs
* Add support for annotating a numeric count on dropdown options
* Annotate parent object on relevant fields
* Improve rendering of color options
* Improve rendering of color options
* Rename option_attrs to context
* Expose option context on ObjectVar for custom scripts
* Document dropdown context variables