Additional category admin hooks to allow alternate category admin interface

[alexkingorg]

Per conversation with Ryan, the following hooks allow me to implement an alternate category admin interface for managing categories - one that works better when there is a *large* volume of categories.

Fewer changes were needed than I expected - only 3 new hooks.

[alexkingorg]

patch

[mdawaffe]

Why not just add a filter the output of _cat_row() instead of the whole shebang? You'd not need to output buffer.

[alexkingorg]

If you only filter the output of _cat_row(), you can't replace the entire list and you are bound by the loop behavior in cat_row(). I need to replace the entire thing.

[matt]

1

[ryan]

(In [4595]) Hooks needed to allow alternate category admin inteface. Props alexkingorg. fixes #3408