There should be more error checking for various things, in particular 
sanity checking of the form variables passed in.

Could check username/password submitted against horde's copy of them
to make sure they match and if not reject it earlier.  Instead we are 
currently waiting until the ftp connection fails to see if the password 
is wrong.  This isn't very precise as the ftp connection could have 
failed for other reasons.  Would need an exception for administrators
changing other people's accounts.

Have not tested changing passwords for others.  Should at least add
a longer list of accounts that can't be changed for others than what
is there.

Probably should remove config/prefs.php since it doesn't really make sense
to have preferences for this module...
