-Add: InvalidPacketLayout exception.
-Add: add_fields helper function to add multiple fields.

Unlikely to be used, but still, for form.
-Add: DateField, LoopingField and DictField

Three 'special' case fields
-Change: import the new fields and exceptions.
-Add: Beginning of mapping of the admin protocol.

Receiving part is not (yet) done... and none of it is fully tested (as
tests have not yet been made)