Migration - Image copy is incorrect for STH and CHL telescopes

[genghisken]

When images are copied the MJD is extracted exclusively from the partial MJD embedded in the filename.

This needs to be fixed so that:

• The MJD extract is done primarily from the exposure ID (because STH exposures that start on MJD - 1 are given the obs name of MJD)
• The MJD extract reverts to using the MJD embedded in the first part of the filename if it can't find an exposure ID (as is the case with Pan-STARRS finders).

[genghisken]

Code has been altered to use the exposure name for extraction of the MJD.

if any([x in filename['image_filename'] for x in ['01a', '02a', '03a', '04a']]):
    mjd = filename['image_filename'].split('_')[2][3:8]
else:
    # Use the old way to get the MJD - relevant for finding charts.
    mjd = filename['image_filename'].split('_')[1]
    mjd = mjd.split('.')[0]
imageDestinationDirectoryName = IMAGEROOT_DESTINATION + publicSchema + '/' + mjd