wip:added separate commands for associating/disassociating a client to group

Hi Keith,

Following are the changes made in this pull request

1. Removed clients associating/disassociating from group update.
2. Added separate commands to support associate/disassociate clients to group.

the allowed commands are command=[associateClients, disassociateClients]

I am working on UI to support above changes.
UI changes would be
1. Remove associate/disassociate of clients feature from update group
2. Provide a separate button to associate clients to group
3. In group context, under clients tab, provide "Remove from group" button to disassociate.

Regards
Ashok