Minor tweaks for modest speed up
Minor tweaks for modest speed up

theta now uses a single nest of loops instead of two, obviating the need to store an entire plane of results.
__getitem__ methods for sharray and plane now return the bit as an int rather than as a bitstring. So the computations  (e.g., &, ^) done with those results are builtin rather than bitstring methods.
ms0/crypto,ms0/crypto