Imported hidden categories had the parent category entity id (UUID)
appended to the end of the name, making the category name quite long
and somewhat hard to read.

Remove the entity id from the end, and replace the apostrophe that
divides the master category from the sub category with a forward slash.

This shortens the name, ensuring a better chance that the full
category name fits into the default table cell width.

Co-authored-by: DJ Mountney <david@twkie.net>