Emitting code for bracket statements.
Added return statement parsing.
Emitted code for declaring locals.  Need to add a few methods I have presupposed in context + sort out library import.  But after that, should be ready for beginning of testing.
New emitting code presupposes certain pieces of functionality in context when handling arguments passed in to a function call.  This commit provides them.  See comments in src.
While filling in additional helper functions that the emitter emits
into its code, realized that should not try to copy public arguments
in (would need an active event at that time).  Instead, since the
inside of each function call is copying args anyways, just rely on
that mechanism.
Added a way (and a test for that way) to convert from Waldo data back
into Python data.
Waldo needs to convert its objects back into regular python objects
when external code calls into Waldo and expects a return value.

The previous version of the emitter had "de-waldoified" objects,
however, it did it outside of an event's transaction boundaries.  As
such, the runtime might have handed an incorrect value back to the
user.  This commit solves that problem.  Essentially, pass around a
sentinel indicating whether when we return from an internal method we
need to de-waldoify return values.  Then, while inside transaction,
dewaldoify.