slightly improved report-pre; add TODO for Jacobian

I feel like it's necessary to introduce Jacobians.
wrote the model section

For introducing the models we are wrestling with (C_1(N), C_1(N),
explicit equations of them, etc.), and results in the literature.
move old code out of report.tex

The computational part is now in report-comp.tex, waiting for a clean up
and rewrite.

Robin's previous work is moved to report-staging.tex, since I've no idea
how to integrate them yet. We will figure this out after some
discussion.
sketch the theoretical results section

Wrote the introduction. The meat is not there yet.

The N = 4 case (relying on the PhD thesis of the guy whose name I still
can't recall) is Robin's field of expertise.

The N = 5 case, dealing with the polynomials and curves, is my field of
expertise, and will be populated soon.