[fix bug 907658] Changing GROUPS_PER_PAGE setting to 21.
[fix bug 908059] Group search matches aliases.
[fix bug 909235] Add 'privileged' privacy level.

 - Add 'privileged' system group.
 - Enable 'privileged' privacy level.
[bug 888006] T-shirt backend code.
[bug 900276] Search group urls in admin panel.
Merge pull request #594 from glogiotatidis/900276

[bug 900276] Search group urls in admin panel.
[bug 909369] Add title attribute to mozillian search result.
Merge pull request #595 from glogiotatidis/909369

[bug 909369] Add title attribute to mozillian search result.
Merge pull request #589 from glogiotatidis/907658

907658
[Fix Bug 898026] ask invited users to login
Merge pull request #591 from glogiotatidis/909235

[fix bug 909235] Add 'privileged' privacy level.
Merge pull request #588 from glogiotatidis/908059

908059
Merge pull request #596 from Sancus/handleinvites

[Fix Bug 898026] ask invited users to login
Merge pull request #592 from glogiotatidis/888006

[bug 888006] T-shirt backend code.