Rename observation_id

[javierggt]

Description

This PR follows PR #86. In that PR, a unique identifier for observations (observation_id) was introduced to the mag-stats processing, from command-line arguments to the supplement tables. This renames it to mp_starcat_time.

Rebase and review after #92 is merged

Testing

• Passes unit tests on MacOS, linux, Windows (at least one required)
• Functional testing. I did the same test as in Added a mechanism to set mag_aca and mag_aca_err manually in the supplement, and a unique star-observation ID #86. I checked that the generated obs-status.yml file uses the new label and that the supplement ended up having the table with the new label.

  # set it to import supplement from here
  export AGASC_DIR=`pwd`
  cp $SKA/data/agasc/* .;
  
  # create a list of interesting stars to test
  echo 331751984 > agasc_id # an OK new star
  echo 991559968 >> agasc_id # star fails (anyway there should be a single-star page for this star)
  echo 505545160 >> agasc_id # only one suspect obs (anyway there should be a singla-star page for this star)
  echo 42864776 >> agasc_id # an OK older star that gets updated
  echo 1200760024 >> agasc_id  # one suspect OBS (the suspect OBS should show up in the single-star page)
  echo 314189096 >> agasc_id
  echo 553396016 >> agasc_id
  
  # start with a set of OK stars
  agasc-update-magnitudes --log-level debug --start 2011:151 --stop 2011:152 --report
  agasc-update-magnitudes --log-level debug --start 2019:280 --stop 2019:281 --report
  
  # add the interesting stars, check the report and check the resulting obs_status.yml
  agasc-update-magnitudes --agasc-id-file agasc_id --log-level debug --report
  open supplement_reports/weekly/latest/index.html
  
  # check obs_status.yml, which should include observations, including the observation ID (the date)
  
  # One could update the supplement 'obs' table with this...
  # agasc-update-supplement --obs-status-file obs_status.yml # and check supplement
  
  # but that would not update the existing report. We do the following instead
  # the important thing is that the report directory must be the same, otherwise it does not work
  # the report directory is given by the stop time (this still needs a better approach)
  agasc-update-magnitudes --obs-status-file obs_status.yml --log-level debug --report
  open supplement_reports/weekly/latest/index.html
  # and check supplement
  

Fixes #95

[taldcroft]

Sorry for forcing this detour...