Cleaned up and improved the audio tab.
Fixes#1546. Kind of. There doesn't seem to be much need for a
sample rate selection for our current high-level audio system.
If we implement higher end audio backends in the future (e.g.
ASIO, JACK), those can be given a sample rate setting.
Project items are now represented directly in nodes opening up more versatility and possibilities. This is the first iteration of this and will be buggy. Need to test thoroughly.
The macro defined namespaces confused the hell out of lupdate and more or less broke translations permanently. Looks like the only way we can do it is to have a hardcoded namespace, which goes against my instinct, but honestly how likely is it that we'll change the namespace anyway (I guess forks might want to do it, but that's their problem ;) )
itsmattkc