Basic access to users collection for non-administrators

Users see all other users they have at least one project in common and
can edit their own data.

Change-Id: Ibb57be4d8edf7d19e4c7e3a4d517576bc532862b
SSH keypairs management for non-administrators

Users may see keypairs for all other users and manage their own keypairs.

Change-Id: I697a81cb28e2740d6feaf0cc46b641a41bdf5deb