This implements a changelog generator using the github issues api for a
given milestone release.  It takes the milestone name, grabs all of
the attached issues and prs that have been tagged with the release milestone
and then converts it into a changelog.

Issues are separated out for user/provider oriented issues, and issues
that impact developer or core internals.  It grabs the category of the
issue and converts it into a changelog that follows the structure here:
https://keepachangelog.com/en/1.0.0/

Everything is spat out to stdout so the release changelog version can be
outputted.  People generating the changelog release will need to copy
the output and add it into the CHANGELOG.md file.

An example of generating the changelog is as follows for the 7.0.2
release.
./command-runner -c CreateReleaseChangelog -m "7.0.2" > CHANGELOG.md

Issues are grabbed in batches of 100 issues at a time up to 15 batches
before the request will bail out automatically.  Hopefully we don't have
more than 1500 issues in a single release but if so this will need to be
adjusted.

If for some reason you need to use your own access token you can do so
by specifying the -token parameter in the command.

Following the naming convention in https://keepachangelog.com/en/1.0.0/
this adds in the changelog for the 7.0.2 release.  This is generated
from our milestone issues.

Changed the release change log format to be the new command syntax.