This class handles a list of LDP files. In particular it
allows you to time sort such a list
The Util::EventFileList sub-class does even more specific things
for FITS event files.
This is not much different from the inherited constructor. It also
sets the extension specifier to undef and initializes some internal
things needed for cataloging.
Returns a list of filenames and LDP header times alternating
This can be conveniently turned into a hash.
Returns another file list sorted by the given set of keywords.