Custom post_type permalink editor not operationable

[dd32]

The post permalink editor is currently broken for custom post_types, It does not allow the editing of the Permalink, and displays the "Change Permalinks" button.

Commit that follows implements custom post_type support into the editor.

There is one thing to note however, get_sample_permalink() takes a shortcut with regards to the handling of the %$query_var% token, It mearly replaces it with %postname%. Since this is only used within the get_sample_permalink functions, i felt this was an acceptable solution to avoid handling the custom token in more locations.

[dd32]

(In [13865]) Fix the Permalink editor for custom post_types. Fixes #12742