MDS plot of 1-dimensional features

[azabicki]

Describe the bug
not really a bug, just not that nice... using MDS plot on kinematic features with only 1 dimension, like the "volume_avg" does not make any sense, because then only a 1-dimensional line will be plotted. Also MATLAB gives a warning...

To Reproduce
Steps to reproduce the behavior:

1. use provided SAMI_demo
2. then
   sami.MDSofStimuli(RDMs_idv(7), 'emotion', userOptions);

Expected behavior

• check how many features are going to be plottet
• skip transformation into 2-dim via mdscale()
• maybe new plot design for 1-dim features?