Bug #1006634, part 3

Adds a new profile_url function which respects the cleanurls
configuration, and makes use of this function in many places where the
user's url field is already available:

- Admin user account settings page
- Redirects after inviting/adding users to groups
- Redirects & notifications after accepting/denying friend requests or unfriending
- The name plate in the top right header & small view header
- Online users sideblock
- Display of threaded personal messages

Change-Id: Ia43ae0867af12f6d78c0ad389fae25c58ac69b43
Signed-off-by: Richard Mansfield <richard.mansfield@catalyst.net.nz>