Compose mime-types during the build process

[wpkelso]

Fixes #1274

Compositing is done through a python script located in the new scripts folder in the repo root, called by the meson build file in the mimes directory.

Currently, the script takes a naive approach and makes a couple of key assumptions:

• Both SVGs have the same dimensions
• Both SVGs are aligned correctly already, and there is no intended interleaving of elements between files
• All shapes, paths, defs, etc. do not have id collisions

"generic", "executable", and "package" base shapes are covered. "books" are not. "template" decorations are also added in a second pass.

* The majority of line changes in this PR are artifacts from removing base shapes *

Extras

• Rim light stops have been adjusted to be consistent for the "executable" base

Potential Future Extensions:

• create template files during build process, so everything about them except the decoration is kept consistent with their base file
• target "book" bases as well. This requires manipulating the fill colors of specific elements