UI Improvements for Group Membership Management

After having a look at the sexy new membership management - it's a huge improvement on the old system - there's a few things that need some tidying up before we can ship.

There are three marked-up screens attached. The issues are:

• Whitespace is too large between section header (user members or group members) and the actual members.
• When the add/remove dialog opens, the result header should not be visible. Gives the impression that there are no users to add. Instead there should be text to help the user understand they should search for the users they want to add.
• When you have added/removed users from a group, there's no visual feedback of success. There should be text on the lines of "Users successfully added. Continue adding or close."
• The "Remove" link is obsolete. Having two ways to remove a user is pointless. Remove it
• Group member adding should be through a similar dialog mechanism to user adding.
• The "Update" button does nothing. Lets get rid of it.
• "Add Selected Users" should not be clickable if no users are selected