Improve the "Add gadget" popup

Improve the "Add gadget" popup. Currently it contains only a handful of gadgets. Add more gadget definitions, make the panel scrollable, add ability to filter the gadgets list and or add suggestion box - http://gwt.google.com/samples/Showcase/Showcase.html#!CwSuggestBox
The gadget definitions can be taken from http://goo.gl/nEem2