Add active model suppport
SMTK&CMB now has a concept of active model. Loading, switching and closing model(s)/data would reset the active model correspondingly. A singleton class(qtActiveObjects) is used to store active model.
SMTK side commit: 35a9fff3cf0d2452638849ac220228adc2736000 Merge !546 first.
close #140 (closed)