Move At Least Some Tests to Their Own Repository

     Currently, the first of the beginnings of any tests for a future implementation live in this repository's 'add-preemptive-acceptance-tests' branch. I should move at least some parts of the eventual full test suite out into its own, separate repository that this one and this format's specification could then re-include as a Git submodule or subtree, if not all of them, if none of them turn out to be implementation-dependent/-internal tests instead of implementation-agnostic specification conformance tests.