Add port bound interface

[mbheinen]

All IPF executables use mostly file based input and output with some simple use of bare bones socket I/O for ipfbat to ipfsrv or gui to ipfsrv communication. It would be good to add a port bound protocol (e.g. https, WebSocket, gRPC, other message based protocol) to be able to interact with power flow or transient stability as a containerized service, allowing it to be run in a scalable container environment such as Kubernetes. The biggest challenge will be maintaining state since IPF requires this for its interaction model. This can be handled in the obvious 12 factor app way of treating it as attached resource (NAS, GlusterFS or mongo GridFS are options)

Could use something like libwebsockets and the existing libcflow library to do this.