Add an option to the configuration file for non-Monday report

[psss]

Some teams are filing status reports on another day than on the end of the week. It would be nice to be able to set in the configuration file a decisive day, so that user doesn’t have to apply --since every week.

[originally filed by Matěj Cepl]

[psss]

Attaching the original patch.

0001-Allow-report-week-to-start-on-other-day-than-Monday.txt

[sandrobonazzola]

I think this is kind of covered by #294