Leg notes

[Olly Betts]

Currently NOTE and NOTEALL are documented as for station notes and aren't allowed in contexts where there isn't a single station they apply to, but we could allow them to be used for leg notes in such contexts - e.g.:

*data normal from to tape compass clino note

or in interleaved style:

*data normal station newline tape compass clino note

It'd also possible to have both station and leg notes in interleaved style:

*data normal station note newline tape compass clino note

One thing I wonder is whether to overload note for this, or whether it's better to be make it clearer these are different sorts of note and to add legnote or something.