Sound machine cards

Took the opportunity to rewrite the Recorder sprite card and scripts, to be a bit more Scratch-like and get rid of a superfluous variable. The revised Scratch file is 'en-GB/Term 2/02 Sound machine/For leaders/Scratch files/04-recording-revised.sb' and is also at http://scratch.mit.edu/projects/18385830/ . Yes, it does work.