Reference documentation for changepassword django-admin command added in 1.2

[Russell Keith-Magee]

I agree that documentation here can be improved.

However, changepassword *is* documented. It's just documented as part of contrib.auth -- since that's where it's defined. If you don't have contrib.auth installed, you won't have a changepassword command, either. createsuperuser *should* be in the same category, but isn't; for historical reasons, it's included in the main django-admin docs.

contrib.gis, and contrib.sitemaps also have management commands that should be clearly documented as part of the django-admin docs, but are currently only documented in the the app-specfic docs.

Rather than just put changepassword into the docs under a 'big list of commands', I think we add a new subheading so that we can group commands that are only available when certain apps are installed.

[Ramiro Morales]

(In [14327]) Fixed #14173 -- Added sections about contrib apps-provided commands to django-admin.py docs.

Added documentation about changepassword, pointers to GeoDjango, sitemaps and
staticfiles commands, grouped them by app.

[Ramiro Morales]

(In [14328]) [1.2.X] Fixed #14173 -- Added sections about contrib apps-provided commands to django-admin.py docs.

Added documentation about changepassword, pointers to GeoDjango and sitemaps
commands, grouped them by app.

Backport of [14327] from trunk