Completed feedback insert where the selected workflow consists of a single tuple.

Reduce and Feedback skeletons are not being typechecked at present.
Checked nesting with the system, it apparently works.
Attempt at nesting multiple skeletons; this never finds the last.

Another way of doing it has been thought up.
A workflow with a single seq is typechecked (first and last) using the new method.

This appears to be closer to a proper solution than the original method, also.
Will do the others in the same style incrementally.