Implement mw-ui-modal and remove jquery.ui usage

First version of mw-ui-modal (as flow-ui-modal)
Unit tests for mw-ui-modal
Input expansion double-focus bug fix

Change-Id: I78a700f5b0689960e30473b4a5a123d146d5a8ca
Merge "Implement mw-ui-modal and remove jquery.ui usage"