Release line support model and Git branching model

[Joe Witt <jo...@gmail.com>]

Team,

There have been a couple lively threads on the subject [1][2] and we
need to get these things documented so we have some shared framework
to work from and we can tweak as needed.  I've tried to distill the
discussion in [1] and [2] and captured from our recent practices the
model as it is today.

Assuming lazy consensus I have documented the model's we're following [3].

[1] https://s.apache.org/FgG2

[2] https://s.apache.org/0zf5

[3] https://cwiki.apache.org/confluence/display/NIFI/Git+Branching+and+Release+Line+Management

Thanks
Joe