Enable local site generation #144
Description
This also enables creating a new user-defined "site" to use adhoc for any image, and also acts as a source of truth for getting a new siteid easily, since it contains the parameters we require in the flows DB.
The Site can also be gotten from astropy EarthLocation, which means we can hook into an existing database/repo/api of Site locations and have all astronomical sites defined by default.
This will also go part of the ways toward enabling a fully local pipeline.