* Major re-haul to `view_each` procedures, which now can loop through selected
  objects, or through files on disk. New versions also implement experimental
  ad-hoc hooks for Praat, which means they can be more easily `include`ed and
  used in other scripts. Both are now available through the menu.

* Modified RMS-normalisation script (changin the arguments as well) so that now
  a target intensity (in dB) is set, and sounds are normalised to that level.
  If this causes clipping, the target level is reduced to a safe level, and
  this new level is reported.

* New procedure: `extract_strings`

* Changes to `extract_labels` now allows use of a regular expression.

* Simplified arguments to `move_to_zero_crossings`.