don't store content message in Content frame

the message was being needlessly duplicated into the Content frame,
now we only store the size there to be sent out, rather than the whole
message

remove QAMQP prefix in authenticator
refactor type handling in QAMQP

There are two distinctive type sets in AMQP, the basic AMQP types
and then the superset of Table value types. This commit attempts to
make that distinction more clear by the addition of a Table class.
Basically, AMQP value type read/write support is left in Frame for the
time being, while table value field read/write support has been moved
to the Table class. Also, a number of type differences exist between
the spec and rabbitmq's binary parser (noted in the errata page) which
were not previously honored.
add autotest for message properties

enhance test coverage around message properties, allowing for better
refactoring of the properties in general.
initialize network variables

there were a number of variables copied over from the legacy Network
class that were not properly initialized.