BUILD Dictionary vs factory functions: doc the class, not the factory

Wondering why the docs for 'bundle' say 'Return a factory method that can
create bundles rooted at the parse context path.' ? This is why.

This change...
Before, any method tagged with @manual.builddict() got pulled into the
BUILD Dictionary. This change introduces a param: now to pull in a
method, decorate it @manual.builddict(show_param=True).

And introduce another @manaul.builddict() param, factory. The builddict
goal, if it sees a symbol tagged @manual.builddict(factory=True), hopes
the factory is a class method and doc's the attached class instead of
the factory function itself.