Remove detect_type from various models

The `detect_type` method is no longer necessary with new_with_type_sti_mixin.

However, removing `detect_type` requires that *all* EMS Refreshers set the type
attribute for all STI objects.

* removes `detect_type`
* removes `default_type` for all models
* ensures that all refreshers set :type
* removes all references to `detect_type`
* removes all references to `default_type`

EDIT by @Fryguy: Needed to avoid the hackery in #481 .