Working, but ugly, data plot in MS_pole

This only works for S-wave data at the
moment and needs significant cleanup. For
example use:

[C r] = MS_elasticDB('ol')
MS_plot(C, r, 'sdata', ...
    [0 90 180 270 10 100 190 280 350 80 170 260 0 90 180 270 180], ...
    [45 45 45 45 60 60 60 60 60 60 60 60 0 0 0 0 90], ...
    [90 90 90 90 0 0 0 0 0 0 0 0 90 90 90 90 90], ...
    [2 4 8 10 2 4 8 10 2 4 8 10 2 4 8 10 16], 'plotmap', {'avspol'})

arguments after 'sdata' are arrays of azi, inc, pol and magnitude,
respectivly.
Plot pdata on MS_pole

e.g. can do:
MS_plot(C, r, 'pdata', ...
    [0 90 180 270 10 100 190 280 350 80 170 260 0 90 180 270 180],...
    [45 45 45 45 60 60 60 60 60 60 60 60 0 0 0 0 90], ...
    [8 8.5 9.0 9.5 8 8.5 9.0 9.5 8 8.5 9.0 9.5 8 8.5 9.0 9.5 8], ...
    'sdata', ...
    [0 90 180 270 10 100 190 280 350 80 170 260 0 90 180 270 180], ...
    [45 45 45 45 60 60 60 60 60 60 60 60 0 0 0 0 90], ...
    [90 90 90 90 0 0 0 0 0 0 0 0 90 90 90 90 90], ...
    [2 4 8 10 2 4 8 10 2 4 8 10 2 4 8 10 16], ...
    'plotmap', {'vp' 'avspol'})
Add docs and runtime input checks for plot data
Turn on the last few effective splitting tests.