WyC: Updated sublist operator for #418

The sublist operator now correctly handles the distinction between lists
and strings, which was exposed by #418.
WyC: AllValidTests are now passing.  #418

Unfortunately, there are still changes to push through.  Some invalid
tests are not passing, and WyJC doesn't compile.
WyC: AllInvalidTests now pass #418.

Updated test cases which were invalidated by the loss of implicit
coercions.  Most of the updates involved putting explicit casts in place
of previously implicit ones.