Updated code review policies posted on OpenJFX Project Wiki

[Kevin Rushforth]

The updated code review policies that we discussed last spring are now 
posted on the OpenJFX Project Wiki [1]. For the most part, we have 
effectively been following these for the past several months. This will 
formalize the policies in a way that will be easier to point new 
contributors at. If any of you have any suggestions for making it easier 
to understand, please send them our way.

The executive summary is:

1. Recorded the fact that Johan and I are co-leads of the OpenJFX Project

2. Formalized the concept of a Reviewer role and recorded the initial 
list of Reviewers

3. Formalized the code review requirements:
* simple fixes: 1"R"eviewer
* higher-impact fixes: 2 reviewers (one of whom must be "R"eviewer)
* new features / API changes: discus proposed changes on this list, CSR 
review (including approval by a Lead) for API changes + 2 reviewers for 
implementation

4. Formalized the streamlined GitHub code review (as long as you 
complete all review steps, including RFR email to this list, prior to PR 
being merged, there is no need for a webrev or additional review to push 
it to HG jfx-dev repo)

I am working on an update to the GitHub CONTRIBUTING.md page [2] to 
align with these newly-formalized policies, primarily to help first time 
contributors, but also as a reminder for all contributors. I'll send a 
PR when ready (tomorrow or Monday).

-- Kevin

[1] https://wiki.openjdk.java.net/display/OpenJFX/Code+Reviews
[2] 
https://github.com/javafxports/openjdk-jfx/blob/develop/.github/CONTRIBUTING.md