SubmitterColumn now links to local site user view when appropriate
SubmitterColumn now links to local site user view when appropriate

In Review Board 2.5, the datagrids were redesigned. However, this broke
the existing behaviour of the submitter column linking to the local site
user page when it was viewed under a local site. This patch fixes that
behaviour.

Testing Done:
- Tested this patch with a local site. Verified that the link in the
  `SubmitterColumn` in the datagrid was to the user view on the local
  site.
- Verified that the link goes to the global user view when not viewed on
  a local site.
- Ran unit tests.

Reviewed at https://reviews.reviewboard.org/r/8241/

reviewboard/reviewboard,chipx86/reviewboard,davidt/reviewboard,sgallagher/reviewboard,brennie/reviewboard,reviewboard/reviewboard,brennie/reviewboard,sgallagher/reviewboard,reviewboard/reviewboard,chipx86/reviewboard,davidt/reviewboard,chipx86/reviewboard,sgallagher/reviewboard,davidt/reviewboard,sgallagher/reviewboard,chipx86/reviewboard,davidt/reviewboard,brennie/reviewboard,brennie/reviewboard,reviewboard/reviewboard