parse-wormedit: peaworm level variant for v90 strings

parse-wormedit: peaworm level variant for v90 strings

The earliest level strings have peaworm levels distinct from multiplayer
levels (i.e. declares 1 worm position instead of 4).

Leave out unsupported level variants in normal output, because having
a 'Peaworm (invalid)' for modern versions would be confusing (and it's
only obvious to leave out undefined data).