Write standalone directory document signature verification tools
Right now, the only easy way for researchers to verify that they are using the actual Tor network consensuses/votes/descriptors is to verify Karsten's OpenPGP signature of the tarball (if there is one). Tor already contains code to verify those documents which have signatures; we should expose that code to researchers' scripts, too.
The extra-info descriptors and microdescriptors are authenticated by having their hashes published in other documents, rather than being signed directly, so they will be a bit trickier for simple tools to verify; we should postpone writing verification tools for those documents for now.