Implemented: FS#560 - Add support for APS (Application Packaging Standard)

- Added Tipsy (http://onehackoranother.com/projects/jquery/tipsy/) so that one can create tooltips for additional explanations easily.

- Added check so that the client password isn't inserted into the message (for security reasons).

- Added circle access control so that 1) a reseller can create circles that contain only his clients, not all clients, and 2) a reseller can send messages only to his own circles instead of all circles.

- Added group (we call groups "circles" so that users don't mix them up with user groups) feature to client messaging section so that messages can be sent to either all clients/resellers or to groups of clients/resellers. TODO: add circle access control so that 1) a reseller can create circles that contain only his clients, not all clients, and 2) a reseller can send messages only to his own circles instead of all circles.

lossless compression of all images of the default themes by yahoo smush.it -> saving 36% ~ 500kb of 1350kb