Maintenance by @bb010g

[roberth]

Hi @bb010g, I've cherry-picked some of your commits from #183. Is that ok?

I have not included the following commits:

• dev: Enhance debugging tools: I believe this is covered by c3290e4a60e83d3f2b285f3ca9bc04e5fa7d1a32
• dev: Expose module options in REPL: same
• dev/tests: Mock callFlake in eval tests: skipped for now, because I wasn't sure about the test suite changes, as they appeared to be tailored (too much?) to the problem at hand
• dev/tests: Implement stronger flake mocking tests: don't quite understand the necessity
• _lib/mkFlake: Document _file infinite recursion_: solved! :tada:

I might have another look at the testing, if you think those changes are useful, but for a first step, here's some of your commits I could merge right away. (And one of mine I guess)