* add ['GalleryView'].getModelsForPeriod() to helper

* models.Hiddenshot will inherit requestPage from parent Shot,
** required for getModelsForPeriod()
* Page['GalleryView'].renderBody() will call layoutPage()
* use parseInt(requestPage) in parse

TODO: layoutPage() should return a dfd
Debug GC.init(), pass null for models

parseInt(requestPage)
added _debounceByArgs() method to GV for use with GV.layoutPage()
apply renderViewport() to Timeline

refactor