interval_to_endpoints: Fix error reporting
FastPiecewise.__init__: Add failing doctest
FastPiecewise.__init__: Fix failing doctest
Add doctests for bug_examples.sage
Accept old-fashioned singletons in FastPiecewise and in scan_functions. New function coho_interval_from_interval
New functions coho_intervals_intersecting, coho_intervals_intersecting_full_dimensionally
lift: New parameter which_perturbation
Rewrite moves code using coho_intervals.  Remove 'interior intersections' hack.
Create functional directed moves from 0-dimensional faces. Fixes testcase example7slopecoarse2
reduce_with_dense_moves: Adjust doctests to new output with coho intervals