make sure to doc the user fields vs. profile module options for d7 admins

mental note to write docs for this (came up in IRC tonight and i wasn't aware of it) - you can add fields to user profiles via both profile and user settings (field api) in d7. need to make sure to write up some docs about the 2 options and implications of each, as i'm sure it'll confuse users.

notes from irc:

adding fields to users ala admin -> config -> users -> fields works for sites with modest needs, and is probably what contrib will base their work off of. But if you need a quick and dirty profile solution with browsing pages, etc. the core Profile module works. Same as we don't *seriuosly* recommend Blog module for anything, but it's there if it works for you. The main disadvantage is that there will probably be a whole whack of contrib modules that build off the Fields/Entities system, and if you're using Profile module you're going to be SOL which is why the official line is "only if it works for you out of the box, otherwise, turn to contrib"