XD-1521, XD-1515: Introduce constant for xd.stream.name and the like

@markfisher This is the first step of what we discussed. I am 

- [x] not changing to xd.job.name for now because there are a handful of test failures I need to investigate
- [ ] not removing Module.addProperties() just yet because other parts of the system still expect it
- [x] not able to provide the UUID out of appContext().getId(), at least in standalone mode. Where is it?