Begin implementing weekly
Refactored policies for easier testing and maintainability

By having objects per-policy, it makes it much easier to maintain each
policy. In effect, each policy votes on whether to keep or delete a
filename. If all policies vote to delete a file, then it will be
reported as deleteable.

This change means we don't do stream processing anymore: the total
result set is read in memory all at once and processed then reported.
The system does not do stream processing anymore.
Extracted common policy for ease of maintenance
Fixed date object not required by default
Prepare version 0.8.0
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