Create standard way for handling large, immutable resource files

[MWYang]

Problem
It would be great if there was a standard way of downloading resource files at build time so that we can avoid checking large text files into this repo, as #428 does.

Solution
Use gradle (perhaps following the solution here) to download large resource files at build time and put them in the correct place. For instance, the large files that are introduced in #428 are also maintained (by me) on a separate repository.