Show pin URL in category listing, order categories, preserve data on errors in /admin/input

* Show pin URL in the category listings
* Show pin URL in the profile lists
* Order categories according to an order requested by David. (will need more work after going live)
* Show items from child categories
* Don't erase form /admin/input/ when errors
* Bigger fields in /admin/input/
* Minor fixes

Please, execute the following in the DB:
* alter table categories add position integer not null default 0;

Note: after you put this to live, please notify me, because I need to enter in the admin and do some changes to the Categories. After these changes I'll request a new server restart.