* Rework the seqmidi aliases.

- The 1st alias is now the Jack1 MIDI port name with alsa_midi prefix.

- This 2nd alias is basically the same as the 1st alias with the
  alsa_midi prefix stripped, so that devices are listed under the ALSA
  names.

Also fixed the "capture" and "playback" port type names which were the
wrong way round.

* Rework the rawmidi alias.

Like in alsa_seqmidi.c, the 1st alias is now the Jack1 MIDI port name
with alsa_midi prefix.

* Rework pretty-name metadata.

The rawmidi and seqmidi pretty-name metadata now uses the same Jack1
port name as the 1st alias, without the alsa_midi: prefix.