Boards with nothing on some layers should have at least something to prevent fab confusion

[sphawes]

Version Number

v1.0.1

Bugfix or Enhancement

Enhancement

Description

Some board shops glitch out when there are layers with absolutely nothing on them, sometimes just fully inverting the layer or putting soldermask nowhere when the intention was to have it everywhere.

Suggested Solution

We should add a small token shape on each layer in an inconsequential place to help board fabs better understand what we're looking to have made.