This was originally just about getting rid of the resource leak.
Turned out to include a little refactoring to hide most of the
UnoDialog member variables.

* use cppu::component_getFactoryHelper
* free leaked createPeer resources in destructor

Change-Id: I45449c49e32af4935908b801ed9bd9732af944d3
Reviewed-on: https://gerrit.libreoffice.org/73565
Tested-by: Jenkins
Reviewed-by: Jan-Marek Glogowski <glogow@fbihome.de>