Move over to using MPR archives

[hwittenborn]

Hey! The MPR's RPC interface is currently in a deprecation phase, and I plan on removing it sometime in the future, and I was wondering if you could migrate over to using the package archives instead, which is the currently supported method for getting package information.

I know we've discussed a little bit on Discord about removing the helper list once Mist becomes a good helper - do you have any plans for that in regards to this repository? If you'd want to just link to Mist or something (once it has all the needed functionality) then you wouldn't need to migrate much, though that's all up to you.

Just throwing this all out there so I can figure out what needs to be done. There's some legacy code in the MPR that'd I'd like remove, but some of that includes RPC code and I can't quite remove that stuff yet.