Alter auto-subclass syntax

Allow 'Object x' in search paths to be expressed as just 'x'

Have a convenient explicit syntax for subclassing.  Or not subclassing.  That is, have "Number x" mean just Number, and "[Number] x" or "Number+ x" mean that and subclasses.  Or have subclassing be the default, and "only Number x" mean no subclassing.
