PSM v1.0.0

Initial version, now stripped down to only 3V3 and 5V.

The digikey order list is attached, but:

• The buck converter + inductor combo that @FilipKus designed the board isn't our standard parts (anymore?), so we'll have to either swap it out for some parts in stock, or bite the bullet
• The switches used are the cheapest of the type, but are expensive in sum
• We're out of stock of the 2.54mm Endurasat headers, but the official ones are ridiculously expensive. Don't order the official ones. Not sure the best way to source some good-enough equivalents.