Abstract interface for Profinet drivers

[shaun-edwards]

The current driver is specific to the Siemens CP 1616 ethernet card. While this card is full featured, a standard Ethernet card should be able to be used for simple IO control. In order to achieve this an abstraction layer should be implemented that would allow common ROS nodes to link against different drivers. This development would be independent of Siemens and should be put in a common repo, here