Revert back to returning GLWidget as default widget
Revert back to returning GLWidget as default widget

Change-Id: Ifcf631faa47d5ed2bbc38a4c4695d3ce74106c0a

ghutchis/avogadroapp,OpenChemistry/avogadroapp,wadejong/avogadroapp,OpenChemistry/avogadroapp,wadejong/avogadroapp,OpenChemistry/avogadroapp,ghutchis/avogadroapp,ghutchis/avogadroapp,OpenChemistry/avogadroapp,wadejong/avogadroapp,ghutchis/avogadroapp