UI: Ginger User Management

This patch added the User Management function to Ginger. "Name",
"Password", "Group" and "Profile" are required for this session. Also,
there are "Add", "Detach" function for user management.

Signed-off-by: Wen Wang <wenwang@linux.vnet.ibm.com>
Reviewed-by: Rodrigo Trujillo <rodrigo.trujillo@linux.vnet.ibm.com>
Tested-by: Rodrigo Trujillo <rodrigo.trujillo@linux.vnet.ibm.com>