Enable use of custom APIs

[cvolkernick]

It would be great to further extend the current option to swap between Helium Inc. & Stakejoy target APIs. Would seem to be a good effort/payoff tradeoff as it gives the ability & reason for more members of the community to get involved with additional private/public instances & take load off public instances.

As an example, HotspotRF currently offers ETL access with site subscriptions -- others could use a service like this or offer similar services which would create a competitive market for cost efficiencies & performance on this front.

As API has been causing a lot of user experience issues as of late, so could be especially beneficial.