Fix "manage" links in new admin to use SITE_ROOT
Fix "manage" links in new admin to use SITE_ROOT

In the new admin implementation, the links for managing users, review groups,
default reviewers and repositories were absolute to /admin/..., which broke if
the site was deployed with a SITE_ROOT. This relatively trivial change adds
SITE_ROOT to the template so that URLs will be correct.

Fixes bug 2404.

Khan/reviewboard,1tush/reviewboard,chipx86/reviewboard,davidt/reviewboard,Khan/reviewboard,atagar/ReviewBoard,1tush/reviewboard,1tush/reviewboard,KnowNo/reviewboard,1tush/reviewboard,Khan/reviewboard,sgallagher/reviewboard,davidt/reviewboard,KnowNo/reviewboard,atagar/ReviewBoard,custode/reviewboard,Khan/reviewboard,custode/reviewboard,sgallagher/reviewboard,brennie/reviewboard,atagar/ReviewBoard,davidt/reviewboard,chipx86/reviewboard,atagar/ReviewBoard,beol/reviewboard,reviewboard/reviewboard,beol/reviewboard,1tush/reviewboard,atagar/ReviewBoard,beol/reviewboard,bkochendorfer/reviewboard,atagar/ReviewBoard,Khan/reviewboard,Khan/reviewboard,chipx86/reviewboard,reviewboard/reviewboard,1tush/reviewboard,1tush/reviewboard,custode/reviewboard,bkochendorfer/reviewboard,custode/reviewboard,atagar/ReviewBoard,reviewboard/reviewboard,KnowNo/reviewboard,Khan/reviewboard,chipx86/reviewboard,Khan/reviewboard,brennie/reviewboard,beol/reviewboard,davidt/reviewboard,brennie/reviewboard,bkochendorfer/reviewboard,brennie/reviewboard,sgallagher/reviewboard,reviewboard/reviewboard,atagar/ReviewBoard,1tush/reviewboard,sgallagher/reviewboard,KnowNo/reviewboard,Khan/reviewboard,bkochendorfer/reviewboard,atagar/ReviewBoard,1tush/reviewboard