initial PickList widget implementation
renamed NameValuePair to NameValuePairImpl due to google's naming convention
renamed INameValuePair to NameValuePair due to google's naming convention
addElement method implementation which provides adding elements 1 by 1 into the listbox
added some getter and utility methods
addel labels above listboxes,
initialize cellpadding between cells to look better
fixed selection bug when last item in the list is moved to the other list.
added PickList component example
added header
Merge pull request #443 from hkarakose/master

initial PickList widget implementation