Use Klar for Container Scanning

Klar is a simple tool to analyze images stored in a private or public Docker registry for security vulnerabilities using Clair https://github.com/coreos/clair. Klar is designed to be used as an integration tool so it relies on enviroment variables. It's a single binary which requires no dependencies.

Klar serves as a client which coordinates the image checks between the Docker registry and Clair.

We can consider if this is better than the current implementation of Clair we're using.