An API for using MQTT over multiple transports

Dependencies:   FP MQTTPacket

Dependents:   Cellular_HelloMQTT IoTStarterKit GSwifiInterface_HelloMQTT IBMIoTClientEthernetExample ... more

Replace 'EthernetInterface' with 'NetworkInterface'

Use ' NetworkInterface' rather than 'EthernetInterface' in MQTTSocket to allow use of other types of network interfaces

MQTT Fork for NetworkInterface fix