Application poms

[romain-grecourt]

Application poms:

Create a new parent pom hierarchy to fit new applications-pom:

• helidon-parent -> helidon-bom -> helidon-3rdparty -> helidon-project
• helidon-parent -> helidon-bom -> helidon-3rdparty -> applications-project

The BOM pom is now inherited by helidon-project, thus the requirement of ${project.version} for
Helidon modules is effectively dropped. This also helps enforcing that the BOM pom contains an entry
for all modules.

Update bare archetypes and all examples/apps to use the application-poms.

Using <relativePath>../../../applications/se/pom.xml</relativePath> in all examples in order
to build locally with a single Maven reactor. This shall be refactored to when
the example are moved out of the main repository. This is a temporary trade-off. Also Updated
the archetype creation script to replace relativePath to <relativePath/>.

Example updates:

• Updated all Dockerfiles to use the new multi-stage docker build style.
• Refactored the webserver translator app to fit under examples, as a two modules backend/frontend project.
• Refactored the todo frontend to use webpack to create nice javascript and avoid serving node_module to the browser...
• Created examples/k8s with shared Kubernetes resources yaml files for nginx-ingress and zipkin.
• Updated all README.md for consistency and add missing details for trying the endpoints / exercising the examples
• Tested all updates

Metrics 2 changes

Simplified the Maven aspect of the metrics 2 support:

• the microprofile-metrics-api dependency is NOT managed ; otherwise the managed version is always enforced, and the
  transitive dependency version is trumped.
• created two properties named after each version of the spec to use to declare a dependency on the API ; this is to be as explicit as possible
• removed all superfluous declaration to the microprofile-metrics-api in order to resolve it transitively from helidon-metrics and helidon-metrics2

[ljnelson]

I like this a great deal.

[tomas-langer]

Approved if all tests pass including native-image

[romain-grecourt]

A couple of non critical changes are missing from this PR:

• a change in etc/scripts/release.sh to update the versions (needs to be fired from parent/pom.xml instead of from the top level pom)
• Add missing <build></build> in tests/integration/native-image/se-1/pom.xml`. I've tested the native-image it works.

Both of these changes will be added directly in the release branch and merged to master post release.