[hlx build] Create openwhisk action from templates

[tripodsan]

As explained in adobe/parcel-plugin-htl#22, the parcel plugin will only be responsible to create the template that renders the resource.

the build process will be responsible to setup the pipeline, wire the pre and wrap it up as openwhisk action. this will allow to:

• remove complexity and delivery domain logic from the parcel plugin
• be flexible about what function to generate (openwhisk, lambda, azure)
• turn the pre.js into a real pre function in the pipeline (nice to have)