Added delete package logic. Upon delete, mirror json is updated to capture
deleted time

Tested it using a couple of local feeds 1 as source and 1 as the destination
1) Refactored DeletePackage into a different method. If there is a 409 conflict, currently, we skip stating that the mirror already has the package
If the package in the mirror has a different SourcePublished than the one from the source,
then, that implies a delete and add on the package. This method will be used then to delete the old package
from the mirror and add back the new one

2) Added $orderby=Published to the "Count" query as well to achieve precision in the results