[defect/#192] `datetime.datetime` not comparable to `datetime.date`
[defect/#192] `datetime.datetime` not comparable to `datetime.date`

Parsing `date` types MUST return `date` objects -- not `datetime` -- else
comparing with they're own `cls.Attributes` will throw an exception.

Also adds support for the previously unused `cls.Attributes.format`.

arskom/spyne,arskom/spyne,arskom/spyne