Services: Documentation and config

[aomarks]

First of a series of PRs to implement services.

This just documents the feature and adds the config field.

Note this PR is merging into the service branch, where I'll be staging this feature until everything is ready (in case we need to release something in the meantime).

[rictic]

Nice design

I can imagine potential improvements, like a way for wireit to communicate with a running service process (to indicate things like when the service is ready, etc), but those would be optional if added, and they might not be worth the complexity

[rictic]

as they depended upon -> as they are depended upon

[aomarks]

Done

[aomarks]

I can imagine potential improvements, like a way for wireit to communicate with a running service process (to indicate things like when the service is ready, etc), but those would be optional if added, and they might not be worth the complexity

Yeah -- I think we probably should include a waitForLog or similar feature to check for a string or pattern on stdout/stderr, since that's pretty simple and will cover a lot of use-cases where you need to wait for a server to be fully started after it's spawned. E.g. "waitForLog": "server listening"