Tracker: Map collision hashes

[pyroscope]

Goal: Load and track multiple metafiles having the same hash, safely.

• Manipulate 2nd metafile: info.x_infohash = __hash__
• Now it has its own hash, load it
• Change download::hash to deliver the alternative hash
• Define a primary_key() method that always delivers the "real" hash, and use it at “appropriate” code locations. Alternativly: deliver value of a primary_key field added to metafile, and the hash if not present. Might need less changes.

In any case, be very sure to not mix stuff up.