Fix some 64-bit to 32-bit shortening warnings
neo_hookean: Energy should be zero at no deformation
Very broken tube bending simulation

Baking the initial guess deformation doesn't work at all, since
if (for example) it goes back to the rest state the result looks
terrible.  Luckily Nathan just added support for varying boundary
conditions to PetIGA, so I'll use that next.
Tube bending works