knative - allow anonymous invocation via PATCH, HEAD, OPTIONS

Actions can be invoked via one of HTTP GET, PUT, DELETE, and POST. We are also looking at invocation using any one of these methods: PATCH, HEAD, and OPTIONS. Also, add a test case for each method by adding it to build.yaml and payload.

We have an example of `OPTIONS` method:

https://github.com/apache/incubator-openwhisk/blob/master/docs/webactions.md#options-requests