Generic Views

I've converted views to the django's generic views mixin style, which brings great advantages:
* views are now consistent with django style
* can be customized easily without completely overriding View classes
* mixin is possible with already existing Generic Views in other apps
* different Paginator class can be specified without even creating a new View class (by passing as a kwarg)
* completely backward compatible (maybe except unused method build_page and context_class property)