updating the prepare.gatherreleasenotes.msbuild script to handle the different allowed issue trackers
Fixing the NuGet packaging script to escape characters in the release notes that have special meaning in XML (i.e. &, ", ', <, >)

#8
Adding the release note properties to the sample settings.props

#8
Updating the nBuildKit settings.props with the values needed to gather release notes.

#8
Updating the AppVeyor configuration with the environment value for the GitHubToken so that we can get release notes for the nBuildKit builds.

#8
Merge pull request #8 from pvandervelde/issue/releasenotes

MsBuild: Generation of releasenotes need to be pointed to correct issue tracker