make client implementation transport and codec independent

[davidtorellineueda]

This story is about decoupling the transport and codec from the client.
The motivation for this is to write clients that can be reused for different transports and codecs by just changing the configuration.

XML changes required

Define the transportImpl and codecImpl at client xml object.

See an example below for the Fix client with quickfixj transport and codec:

            <client impl = "com.neueda.etiqet.fix.client.FixClient"
                    transportImpl = "com.neueda.etiqet.transport.qfj.QfjTransport"
                    codecImpl = "com.neueda.etiqet.transport.qfj.QfjCodec"
                    defaultConfig="${user.dir}/src/test/resources/config/client.cfg">
                    ...

Now, considering that we want the Fix client to use Rabbit MQ transport and Google Protocol Buffers codec, we could define this other client configuration:

            <client impl = "com.neueda.etiqet.fix.client.FixClient"
                    transportImpl = "com.neueda.etiqet.transport.rabbitmq.RabbitMqTransport"
                    codecImpl = "com.neueda.etiqet.transport.gpb.GpbCodec"
                    defaultConfig="${user.dir}/src/test/resources/config/client.cfg">
                    ...