fixed & tweaked Vorp audio

Fixed gain node creation names to keep up with WebAudio spec.
Also adjusted tractor beam hold sound to be less dental-drill, more
birdsong
teeny jsdoc tweak
Removed chronic error creation onload

The base64 lib I borrowed created and cached an error. That would halt
debuggers onpageload if they were set to halt even on caught
exceptions. Now we only create errors when it’s time to throw.