Add project doctor facility [WIP]

[grayside]

Here's another change in the direction of facilitating automated support for projects: a system for project-specific doctor checks. Currently the system works fine for declared "conditions" in code, the next steps are:

• Create some built-in checks based on the outrigger.yml configuration and/or other parts of rig such as project_sync.go:GetVolumeName().
• Merge in a top-level doctor key as described in rig project doctor #58 to allow generator/projects to add docker-compose config validation and whatever other environmental checks they want that are not better off as automated tests.

[grayside]

Rebuilt this, new PR inbound.