Previously, Frames could set both these properties along with a
thickness to confusing effect: Most shapes of the same shadowing only
differentiated at a thickness >= 2, and some not at all. This led
to a lot of creative but ultimately superfluous choices in the code.
Instead let's streamline our options, automate thickness, and get
the right look without so much guesswork.
Plain shadowing has been consolidated into a single Plain style,
and 0 thickness can be had by setting style to NoFrame.
SPDX License Identifiers are a more compact / standardized
way of representing file license information.
See: https://spdx.dev/resources/use/#identifiers
This was done with the `ambr` search and replace tool.
ambr --no-parent-ignore --key-from-file --rep-from-file key.txt rep.txt *
