New subclass selecting and url queriing

Added an fabric function that provides class depending superclass and
dict of properties.
Added ability to add url queries: they are now kwarg in get() or first()
method calls. where kwarg is former result filter. So now
resource.get(where={'data': '21.12.2014'}, filter={'user': 'Boris'})
means that ?user=Boris will be added to url and result resources list
will be filtered for a field data to be '21.12.2014'.