Largely conforming renderers to new NodeValue system. Code seems a lot cleaner
this way which is a nice advantage. Likely non-functional as this won't
compile just yet and still needs probably another day or two of testing to get
it back to where it was before.
Old code assumes that a NodeParam's parent will always be a Node. The function
has been separated off and tweaked in the event that this is not the case.
Since we're now working with a separate proxy copy of the original node graph,
if the user changes a parameter in one of those nodes (triggering an
InvalidateCache signal), the values in our copied graph need to be updated
with these new values too.
Major refactoring work to try sharing as much code as possible between the
video renderers and audio renderers, as well as make them as
platform-independent as possible.
itsmattkc