[#2373] Support datetime for since and until repo-config.csv

[gabriellegtw]

Fixes #2373

Proposed commit message

Support datetime (previously just date) for since and until in repo-config.csv

3 supported formats for since and until dates: 
1. DD/MM/YYYY
2. DD/MM/YYYY'T'HH:mm
3. DD/MM/YYYY'T'HH:mm:ss

Behavior: For since date, if hour/minute/seconds not supplied then
default to 0 for each. For until date, if hour/minute/seconds not
supplied then default to 23, 59, 59 respectively.