Run climate data imports without needing to introduce DB downtime

[CloudNiner]

The DB incurs downtime (~2 mins) during data imports (x2) when we swap the DB instance type and parameter group. This prevents DB writes during import from overwhelming available DB I/O and CPU.

Potential solutions may involve a re-imagining of the DB, or we could just ingest all the data entirely, preventing us from having to do another import. This particular option was requested in azavea/temperate#1135.