[Zope-CMF] better FSDTMLMethod tracebacks

[seb bacon]

Tracebacks from FSDTMLMethod are rubbish at the moment, because the
name of the files in which they occur is obscured by RestrictedDTML.
This can be fixed by adding a self.__name__ = id to the FSObject class
constructor.  Should this be fixed in the CMF, or is this a wider Zope
issue (e.g. DT_* methods should be raising the value id instead of
__name__, or RestrictedDTML should be implemented differently, etc)?

seb