Finish implementation of calibration sequence

Several more features (addressing #13 (closed), #14 (closed) and #19 (closed))

• As a side effect I discovered we are forced to use python 3.7.
• Use glob search to be able to use calibration runs from a different day in case there is no usable DRS4 or calibration run from the same day the data was taken.
• By default calibrationsequence.py will try to produce a new time calibration file every night if possible. Otherwise, a link to the default time calibration file (corresponding to run 1625) will be produced.