Enhance user management / Filter views

[olivewood]

At the moment there's two kind of access : admin / not admin

This is straightforward but it could be really nice to introduce a kind of 'group' concept to limit visible informations

example : - "DB usesr" could be interested only on events related to hosted databases - We could have different teams working on subset of hosts (datacenters...)

it could be a 3 steps configuration : 1 - Admin create groups 2 - Users are assigned to groups 3 - Groups/Viewable items are configured via rules (UI/process could be inspired from the Rules/alert Panel)

[Tildeslash]

Might be added in the future for Monit. Will definitely be added in M/Monit.