Fixed ReqMgr links, user/group priorities removed

- some links to reqmgr/view broken (Template not found) - fixed, offers
  default ReqMgr Browser page
- DAOs, APIs and all related code to user and group priorities completely
  removed, as confirmed by @efajardo, Ops have never used it (and it would
  have hardly worked if they had)
- yuiserver link removed

Someone (@efajardo) should comment if links to GlobalMonitor or broken
"monitorSvc" should be kept on the ReqMgr page.
Merge pull request #4495 from zdenekmaxa/reqmgr-fix-broken-links-user-group-priority-further-removal

Fixed ReqMgr links, user/group priorities removed