bin/map: Only turn on by_col optimization if mapping to same DB, rather than requiring each place that checks by_col to also check whether mapping to same DB

input.Makefile: Testing: Don't abort tester if only staging test fails, in case staging table missing

input.Makefile: Testing: When cleaning up test outputs, remove everything that doesn't end in .ref

input.Makefile: Testing: Added test/import.%.staging.out test to test the staging tables. Sources: cat: Updated Usage comment to include the "inputs/<datasrc>/" prefix the user would need to add when running make.

bin/map: Fixed bug where mapping to same DB wouldn't work because by-column optimization wasn't implemented yet, by turning it off by default and allowing it to be enabled with an env var

bin/map: DB inputs: Use by-column optimization if mapping to same DB (with skeleton code for optimization's implementation)

input.Makefile: Mapping: Use the staging tables instead of any flat files if use_staged is specified

bin/map: Support custom schema name. Support input table/schema override via env vars, in case the map spreadsheet was written for a different input format.

sql.py: qual_name(): Fixed bugs where esc_name() nested func couldn't have same name as outer func, and esc_name() needed to be invoked without the module name because it's in the same module. select(): Support already-escaped table names.

main Makefile: $(psqlAsAdmin): Tell sudo to preserve env vars so PGOPTIONS is passed to psql