[Bug-apl] APL Package Manager preview

[David B. Lamkins]

The APL Package Manager has, over the past week and a half or so,
matured to a point where I believe that it's now suitable for a first
look by interested parties. The external API will evolve, so please
don't use the package manager with the expectation that I won't soon
negate the fruits of your labor. This is still pre-alpha software.

On the other hand, I have added a handful of trivial demo packages that
you may use to bootstrap your experimentation. These will be modified
(with updated APIs), extended (to include other languages and tools) and
documented (I plan to include a tutorial) in the days ahead.

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