Added colnames, rownames methods for nts. Helps workaround a problem
when assigning: dimnames(x) = list(NULL,"abc"), when the data member is
a data.frame.
Got rid of raw and qc arguments. Just plot a profile of a single
sounding. Pass xnames and yname argument instead of plotting all
X columns and having to search for the Y column.
If sdng arg is a list, plot all soundings.
Unit test updates.
plotLimits: remove warning about multiple scales