User and groups/projects support

As an admin I'd like to allow users to have more control of their services. We should be able to:
- assign services to user groups (aka projects)
- services should only be editable by the respective project members and superadmins (aka staff)
- each project should have their custom own dashboard list
- every service and dashboard should have the option to be available to all users in RO mode (or even RW, but that's not a strict requirement)

Agents should be assigned either to everyone or a specific user group, so an admin can restrict access to certain agents.

Feel free to separate this issue into smaller ones if you start working on something.