Add (buggy) support for delaying [sound] tags

This is the initial pass on this, with a few buggy bits:

- keystrokes still trigger the delay
- using the add/edit note window during a review session means anything
  that uses the native sound function (which, as far as I know, is just
  the playback of a newly-inserted sound), will be incorrectly delayed
- filenames that end up with a junky " (1)" filename won't match the
  regex and will not be recognized as AwesomeTTS sounds