Add REST route to be able to search for users

This reuses getPaginatedUsersByUsernameOrRealname introduced for global
search.

Some cleanup: logical order for parameters, dead code removal.

Change-Id: Ief60c87c1d50f909a1b46187a554ce0abee389c8
Convert @mentions into clickable links

This is part of request #7303: Ability to easily reference a user (@mentions)

Change-Id: I3a25d24b0e757a89526a3d8c9697424b313b823d
Merge commit 'refs/changes/46/2746/5' of ssh://gerrit.tuleap.net:29418/tuleap into stable

* ssh://gerrit.tuleap.net:29418/tuleap:
  Add REST route to be able to search for users

Change-Id: Ie9ca7895f045ae5fa105c9dd0b06d16059d42951
This is Tuleap 7.3.99.26

Change-Id: Ie1d7f86c9c2d2b8ac052872902d8fdb1fe3534a1
Merge commit 'refs/changes/45/2745/4' of ssh://gerrit.tuleap.net:29418/tuleap into stable

* ssh://gerrit.tuleap.net:29418/tuleap:
  Convert @mentions into clickable links
This is Tuleap 7.3.99.27

Change-Id: Ifb8baef9ef3d4060711ee301ee2e5c364d893a43