ENH: Give get_iterates maxiter again.
BUG:  LinInterp inverse implementation was buggy.  Removed.
ENH: Add inverse back to lininterp.

I was being silly when I removed it.  Only makes sense to call
inverse on the policy rule.  The value function isnt' going
to give resonable answers since its domain is different.
FIXUP: fixup on bellman doc.  return pr or vf.
BUG: Changed api and missed this change.