Add query filter argument to register_taxonomy

[tifosi]

Following on from the #21240 ticket which introduced the show_admin_column functionality I would like to suggest an additional argument to easily add the select list query filter for a taxonomy to the post-type list.

Currently a taxonomy query can be added via the 'restrict_manage_posts' action and 'parse_query' filter.

It would be useful to add an additional register_taxonomy argument of 'show_column_filter' to define a standard select option list of the taxonomy terms. Things like default option and hierarchy could be optional settings is an array is passed instead of boolean.