Added normalized property to the Path configuration datatype

Ignore-this: bf89d3c8ac1d14bd9dbd204239f45f30

darcs-hash:20100203142944-1e3d8-e05993e99adcb252d0a4a60104cb1c5432ab1b4c
Fixed AccountManager.default_account to allow it to be set to None

Ignore-this: 581c81ace5d1d8466e5b97678b5d6afa

darcs-hash:20100203153403-1e3d8-b64ca19f40797248c992a591abaaf3b92045be8d