This is a generic subroutine meant to serve as a superclass
for subroutines for extracting and plotting lightcurves.
It provides functionality for plotting the lightcurves
This method does nothing. Subclasses should override it.
This method lists all the lightcurves which should be plotted
it defaults to listing all files of type "lightcurve", but subclasses
may override this - particularly if they have more than one subclass
of this class.
Plot all the lightcurves.