rewrite doc
doc updates
execute hook scripts on setup/cleanup
new Track methods: rec_setup_script, rec_cleanup_script: return full path to script
new commands: edit_rec_setup_hook edit_rec_cleanup_hook
Merge branch 'hooks'

Proof of concept. One problem is that we don't know if maybe
our external synth program is already running, in which we don't
need any setup. The full burden of determining this falls
on the scriptwriting user.