Changed names of several functions.
1. lyra_event_list -> make_lyra_flare_list
2. find_lyra_events -> find_lyra_flares
3. extract_combined_lytaf -> get_lytaf_events
3. testing_find_lyra_events -> testing_find_lyra_flares
Changed variables named (or partly named, e.g. clean_flux) flux to
irradiance (or e.g. clean_irradiance).
Changed variables names fluxes (or partly named as above) to channels.
Rewrote _prep_columns to be simpler.  Biggest change was to remove
option of having filecolumns produced automatically.
Rewrote _check_datetime() to be simpler and added use of parse_time()
to convert strings to datetime objects.