knative - allow anonymous invocation via PATCH, HEAD, OPTIONS

[pritidesai]

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