if x has only 1 spectrum, return a matrix with 1 column instead of a vector
extra arguments ignored
If x has organization equal to 'vector' then it returns x,
unless forcemat is TRUE when it returns x as a matrix with 1 column.
If x has any other organization then it returns a matrix
with spectra in the columns.
All of the colorSpec attributes are stripped except the column names,
and the row names are set to as.character(wavelength(x)).