Implement automatic updating of adjacency matrix data

[dondi]

As a follow-up to #951 we would like to eventually build a layer on top of that work which will periodically or manually update adjacency matrix data from their primary source(s). Timestamps will need to be maintained in order to preserve prior downloads, which will promote replicability of study results by ensuring that all data sources remain consistent.

[kdahlquist]

Is this issue still necessary?