Add time sorting of EDF files on load

When files are loaded in, we sort them alphabetically based upon file name. If they were not modified off of the machine, then this will successfully order the files chonologically. If they were renames, then the sorting is not guaranteed to work. The date-time of each case is stored internally in the EDF file.

We should change the sorting from alphabetical to chronological based on the date-time listed in the case. Both date and time are important to prevent bugs when cases pass midnight.