Portland and Tualatin basin data and polygons

Add polygons for Portland and Tualatin basins, as well as Z1.0 and Z2.5 .csv files for each polygon. Z1.0 and Z2.5 data are original data supplied by S. Ahdi - we are not using Z1.0 effective in the Tualatin basin, after sensitivity tests, working group decision, and workshop feedback.

changed milestone to %Finalize draft NSHM 2023

added 2023 label

assigned to @jaltekruse

merged

mentioned in commit 69b50e4c

mentioned in issue #24 (closed)