Add meta class `M_Entry` to set `Kind`
Make `Q_Result.__str__` deterministic

Sort SELECT arguments to ensure deterministic ordering
Add `type_name` to Id_Entity._as_template_elem_inv
Add support for `polymorphic_epk` to `Filter`

and `Filter_Atoms`
Use `af.ui_type_name` in `entity_selector_form`

Add `ui_type_name` to `Id_Entity._as_template_elem` and adapt tests
Move `json.etn` into `if` of `_get_attr_filter`
Split `input` field "__attribute_selector_for__"
Add `__call__`, add argument `proto` to `__init__`
Add polymorphic entity selector <form>

* Factor `GTW.RST.TOP.MOM.Admin._JSON_Action_._get_esf_filter`,
  support `polymorphic_epk`

* Add jinja template macro `entity_selector_form_p`

* Adapt javascript functions in e_type_selector.js to support
  accordion for polymorphic selection

* Add CSS rule `clearfix` to rule for `QR`