Milestone dates for OpenJFX 11 release

[Kevin Rushforth]

We are getting close to the start of rampdown for JDK 11 [1]. Now that 
FX is no longer bundled we don't need to follow exactly the same 
schedule of milestones, although we do want to release this first 
unbundled FX 11 release at the same time JDK 11 ships (or slightly sooner).

Here is the proposed rampdown schedule for FX 11. The main differences 
between the JDK schedule and the FX schedule is that we don't need as 
long a back end as a full JDK feature release

2018-07-09 : RDP1 (aka feature freeze)
2018-08-06 : RDP2
2018-08-27 : freeze for GAC build
2018-09-18 : GA

I am proposing a shorter time after RDP2 than the JDK because I don't 
think we need the long back end of a full JDK feature release (not as 
many moving parts or stakeholders).

I will send out the proposed ramp-down policies, but as a starting point 
I imagine we want something similar to what the JDK uses with a couple 
modifications:

1. Since this is our first unbundled release and there are likely to be 
plenty of bugs that need fixing during RDP1, so I propose to postpone 
forking the repo until RDP1. This means a 4 week downtime where there is 
no place to push new features / enhancements unless they are critical to 
openjfx 11 (in which case they will be an exception). I think this is a 
reasonable trade-off for this release

2. I don't plan to propose any restrictions on P4 bugs before RDP2. The 
focus should be on more serious bugs, and we likely won't fix many P4s, 
but if a safe P4 bug fix is proposed, reviewed, and tested, then I see 
no reason not to take it between RDP1 and RDP2.

-- Kevin

[1] http://openjdk.java.net/projects/jdk/11/