More restructuring on Python config code for auto-generating

More restructuring on Python config code for auto-generating
of Param structs.

objects/CoherenceProtocol.mpy:
objects/Ide.mpy:
    Update for new Enum syntax.
sim/pyconfig/m5config.py:
    More modest restructuring heading for auto-generating
    of param structs.

    - Revamped Enum handling: Enums are regular classes so they
    know their names now (makes it easier for generating C++
    equivalents).

    - Created MetaSimObject class and moved some SimObject-specific
    stuff there (i.e. does not apply to ConfigNodes in general).

--HG--
extra : convert_revision : a93b40dda3b038ebe8bffecac97e9079c22af561