Enhance category sets

[jadO]

The panel category sets only show predefined categories. If there is need to apply a category which has not been put into a group then it does not show up.

Suggestion: Add a category search-as-you-type field (like the one when adding a category to a category group) to quickly access and apply a category from within the panel.
This cone be done like the predefined category sets history, suggested and assigned, but it should read "search" and when I expand it, it should display the search field.