[Bug-apl] Package manager proposal and design sketch

[David B. Lamkins]

See https://github.com/TieDyedDevil/apl-pkg .

This repo has most of the documentation as comments in the code. Read
both .apl files. See additional notes in the README.

There's one very important thing to note: This is not yet a functional
package manager. The primary roadblock is that GNU APL does not (unless
I've overlooked something) have a programmatic equivalent of )copy.