listing children categories when listing a category

i made this this patch to let you see all children when you go to a parent url. for example:

suppose you have a site organized like:

sports
|---ball sports
| |---football
| | |-indoor
| | |-outdoor
| |
| |---baseball
|
|---mind sports
|---chess

you want to point your browser to http://www.example.com/ball-sports
and get all entries in 'ball-sports' but also in 'football' and 'baseball'.

as far as i know, there is no easy way of doing this. so i created this patch.

from the admin page you can check or uncheck a 'show children' checkbox. if unchecked, it remains as always. if checked, it gives you al children when listing a term.

i also modified the database but i'm not sure on how to submit a patch for the mysql table.

you also have to add a column to the table 'vocabulary' named showchildren.