Implement project.json support for bolt test.

@markhibberd similar to last review, for bolt test this time.

Adds project.json support for:
- test.node
  - verbose
  - config
  - tests

Also pulls project.json parsing into a separate module so it can be reused across commands and fixes up various default paths.

One TODO that came out of this is that currently there is no glob support for the "tests" field, which makes it a bit cumbersome to use - you have list every test explicitly, and remember to update it when new tests are added.

I'll file an issue about this. Basically we just need to sort out globbing in general in a bunch of places, so I'm planning to address it all in one go hopefully sometime soon.