refactored/cleaned AdminPage class
changed all instances of Collection::get() with no argument to Collection::getAll()
MVC: default post model is no longer abstract
AdminPage: implemented tabbed navigation
fixes #29
fixed Utils::getControlNamesFromCallable + now Metabox using Utils::getControlNamesFromCallable
changed 'Factory' class name to BebopFactory
Merge branch 'feature/admin-page'