Add additional null checks to metrics script

To avoid exceptions on other pages I have added an additional null
checks to make the script used on the metrics overview more robust.

Signed-off-by: Konrad Reiche <konrad.reiche@gmail.com>
Make the completeness detail view more readable

I have added some styling to the detail view of the completeness metric
detail view. I converted the record keys from snake_case with inflection
to a more human readable format. Also made the table layout more fixed
with fixed sizes where appropriate.

Signed-off-by: Konrad Reiche <konrad.reiche@gmail.com>