WIP infrastructure for "After the current module is loaded,⁇do_".

[markATavail]

WIP!

• New primitive is not tested, do not use it yet.
• "null" path component was showing up when gradle task was copying generated files to destination. I added a null check in the systempath() method, which caught the error. The problem was that at least one top-level val was not initialized, because earlier top-level expressions prior to the uninitialized val were still being initialized. I moved the problematic vals higher in the script, which solved the problem.

[toddATavail]

Superseded by upcoming PR.