render: gst-ffmpef is no more, it is now gst-libav
render: Always iterate on already available elements in encodebin

Because if encodebin.profile.presence is > 0 then the elements are
created right away exposing the pads and all.

This makes sure that the encoders settings are taken into account!
widgets: Implement the DefaultWidget.setToDefault method

Avoiding to raise AttributeError: 'DefaultWidget' object has no
attribute 'setWidgetToDefault' if the user resets default setting on an
element that does has a property type we do not properly handle