Use new release of IdentityModel in DCR sample with extension properties

[josephdecock]

This requires that we do a release of IdentityModel. The issue is that the current latest version of IdentityModel has a bug in DCR documents with extension properties, fixed in https://github.com/IdentityModel/IdentityModel/pull/540. If we release that, we can update this sample to use it as well (and show how to do so).