[heat] Propose retirement of heat-cfnclient

Hello, In heat project, we have had the heat-cfnclient library which contains the client utilities to consume AWS-compatible APIs in heat. However this repository is not properly maintained and I doubt that anyone is using (or even can use) it with recent Heat.  - The repository still contains the utility for CloudWatch API which was already    removed from heat  - The heat-cfn command relies on Keystone v2 instead of v3  - No release has been made since the repository was created Based on the current situation I'd propose retiring the repository. I'd appreciate any feedback and if I hear no objections then I'll start the official process to retire the repository. Thank you, Takashi