Fix computability thy's in light of pat_assum rename

Fix goedelCode example (broken by 5203fc450fa I assume).

Adopt ML-style syntax for case expressions and use freed up "||" for bitwise-or. See issue #24.

src/num/theories/SingleStep.{sig,sml} is gone. The
defininitions of Cases, Cases_on, Induct, Induct_on,
CASE_TAC (and co.) are now in basicProof/BasicProvers.
completeInduct_on and measureInduct_on are now in
numLib. recInduct is now in src/tfl/Induction.sml.
All these are collected in bossLib, so the changes
should be invisible to ordinary users.

SingleStep.*.doc has been changed accordingly.

BasicProvers.NORM_TAC should now automatically perform
all case splits (from if-then-else expressions as
well as case expression) arising anywhere in the goal.

Removed trailing whitespace from all .sml and .sig files.

This affects over 900 files and was done using emacs's delete-trailing-whitespace
function in batch mode. Building the system with Poly/ML and Moscow ML seems to
work, so I'm hoping these changes don't break anything. Please complain if
they do!

Added decoder for Goedel numbers.

Goedel coding of number lists. To be used
to encode register and Turing machines.