Move/remove geo_type, time_type from as_epi_*(); consider requiring other args by name

[brookslogan]

These are hanging around crowding documentation for these functions.

Consider either

• Removing geo_type and time_type from the as_*() functions altogether. Though, it seems like time_type overrides could be useful in epi_archives currently, though perhaps as a workaround for other issues; if we do want these overrides, then we'd want to keep these parameters and add functionality back to them.
• Moving geo_type and time_type to the end of the args list.

Consider also:

• Moving all but the first argument to as_*() functions behind ... so that they must be called by name. This can help enable better error messages in legacy user code still passing *_type arguments positionally. It also may help code to read better.
  • This option is no longer as clean, as ... is not expected to be empty but now powers rename functionality... probably can still be made to work.