Add time intervals to the SCAN-B report

[Nicklas Nordborg]

It would be nice with some information about how long time some things take. There is some space in the footer where we can add:

Days from Arrival to: Sequencing (y), Gene expression (z), RNA-QC (w). Report create date: xxxx-xx-xx

In the version with personal information:

Days from Sampling to: Arrival (x), Sequencing (y), Gene expression (w), RNA-QC (q). Report create date: xxxx-xx-xx

Sequencing date should use the end date.

[Nicklas Nordborg]

In 6256:

Fixes #1308: Add time intervals to the SCAN-B report