WIP: Add ability to deploy some virtual-stbs to a raspberry pi

Useful for stimulating a TV for testing Smart TV support.
WIP: debugging: Log OCR

TODO:

* Tests
WIP: ocr logging: Put in same directory as match logging

The ocr and matches form a narrative, so should be in the same
directory.

TODO:

* Figure out if this is a good idea?
* Remove "detect_match" from directory of both?
stbt-camera-calibrate: Plot measureds on graph rather than deltas
service: Refactor config handling
Fix output from service when using virtual-stb
service: Take default stbt config from /etc/stbt/stbt.conf

This enables customization of video source and lirc config from outside
the container.
virtual-stb: Write IP address of virtual-stb to config

This will allow the virtual-stb to provide additional services, e.g.
enabling the test-pack to grabs logs from the virtual-stb.