JDK 9 Rampdown Phase 1: Process proposal

[Martin Buchholz]

When changes start being rejected, it's time to think about the Next
Release.  Which is especially true when different parts of the project are
maintained by different groups with different schedules.  I recall in past
releases having to save up changes in private repos because jdk-next was
not yet open for business.

Martin's fundamental Law of Software Development:
Developers must always have a place where they can safely submit changes,
managed by competent release engineers.