Update SE restful web service guide and code

[tjquinno]

A number of API and other changes have altered the quick-start code on which the SE restful web service guide is based.

This PR updates the Java code accordingly and also changes the guide so it:

• uses the Helidon Maven archetype to generate the project
• acts mostly as a guided tour of the archetype-generated code, rather than a sequence of copy-and-paste steps by which the reader would construct the app.

The last sections of the guide, as before, show how to modify the app to add an app-specific health check and an app-specific metric.

See issues #214 and #176

[tjquinno]

Note: In the initial creation of the PR I did not do the required preprocessing of the README.adoc file to pre-include all included content. The automatically-run wercker/build job will fail until I change this, but reviewing the changes should be far easier with the natural-style include:: directives rather than the preprocessed form.

[tjquinno]

I've included the preprocessed version of README.adoc because I think that will actually make comparing the edits easier for reviewers. (It also clears the pipeline build error that resulted from using the natural-form instead of the preprocessed-form file.)

[tjquinno]

Note to reviewers: Please don't spend time on the MP README.adoc that is included in this change set. Soon I'll open a separate PR for the MP changes which will be much more extensive than what's shown here. I updated the MP guide as part of this PR so the pipeline build test for the MP guide would pass (because it includes significant portions from the SE guide).

[tjquinno]

Previous commit and push reflect comments about the SE tutorial recorded in PR #367.