Commit Access Policy - draft for comment

[Gervase Markham]

"Currently, Mozilla has a large number of code trees in various source
code management systems, many of which have differing requirements for
access. This is confusing and difficult for both developers and
administrators. This document is the first draft of a vision for what a
unified commit access policy might look like. Having a clear commit
access policy makes the lives of developers and administrators alike
easier."

https://wiki.mozilla.org/Commit_Policy

This is likely to need careful review and improvement; I've been working
on this for a while now but I'm still sure I haven't got it right first
time. Comments welcome.

Gerv