move the conversion stuff that was in configs/kernel/Config.py into

move the conversion stuff that was in configs/kernel/Config.py into
the m5 package as convert.py
add a smartdict class which stores strings and can intelligently
interpret those string variables as several other types.
make the env dict use the smartdict class

python/m5/config.py:
    move a bunch of conversion functions into convert.py
    turn the env dict into a smartdict
    adapt the _CheckedInt stuff to deal with derived types
python/m5/objects/BaseCPU.mpy:
    env is now a smartdict and can properly convert to bool

--HG--
extra : convert_revision : 8abcd35a5ab14b82f280aea59020953869e33365