[fix bug 908059] Group search matches aliases.
[fix bug 909235] Add 'privileged' privacy level.

 - Add 'privileged' system group.
 - Enable 'privileged' privacy level.
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
[Fix Bug 881852] add multi-account field to user profile