Squashed 'External/Expecta/' content from commit 56dcded

git-subtree-dir: External/Expecta
git-subtree-split: 56dcdedde9a0f81b25ba76b8fcbb902dcd4f8135
Merge commit 'a571c2b430c5b6716327e8394dc3d1151d9101d3' as 'External/Expecta'
The test runner tool is copied into the framework bundle.
Tests can be defined taking fptrs, strings, and selectors as subjects.
Expectations produce test results.

This adds Expecta support back.

Closes #5.