Pronserve

This is a new experimental server for Pronsole that replaces the previous web interface.

The reason for a wholesale rewrite of the web interface, while it may seem a drastic measure, was so that the web interface to Pronsole would not be tightly coupled to a single UI and allow for network discoverability. This new code base is designed to be reused by any number of 3rd party user interfaces and/or printer farm automations.

To quickly summarize, this new print server can already:
- be discovered by people on a network using MDNS, the same technology that powers AirPlay
- print parts from a queue (so that multiple users can easily share a single printer)
- present a REST interface to start, pause prints
- present a REST interface to estop
- present a REST interface to add/remove/reorder print jobs in the queue
- present a Web Socket interface to receive printer events

Furthermore Chris (colah) and I are going to use this as a basis for further improvements to Printrun.

In conclusion, I hope you will find the enclosed pull request most seriously Awesome.