Support comparing Id_Entity to query...attr("pid")

* Consider `TFL.Q_Result._Attr_` in `MOM.Id_Entity.__eq__`

* Factor `@_comparison_operator` from `TFL.Q_Result._Attr_`

  To allow mixed numeric comparisons, try normal comparison first.

  Previously comparing a `int` to a float wrapped in a `_Attr_` failed
  even if it should have succeeded!
Test&fix `polymorphic_epk` for query restriction
Add options `-HTML`, `-receiver`, `-subject`