Add PHP 7.3 runtime support to default deployments

[csantanapr]

Title: Add php:7.3 runtime support to default deployments

1. Add php:7.3 to core ansible/vagrant deploy

• Add php:7.3entry into ansible/files/runtimes.json
• Update and add doc file into docs/action_node.md
• Update unicode tests https://github.com/apache/incubator-openwhisk/tree/master/tests/dat/actions/unicode.tests

3. Add php:7.3 to docker-compose deploy

• Add php:7.3 into runtime manifest
  https://github.com/apache/incubator-openwhisk-devtools/blob/master/docker-compose/docker-whisk-controller.env#L64

4. Add php:7.3 to deploy-kube

• Add nphp:7.3 into runtime manifest
  https://github.com/apache/incubator-openwhisk-deploy-kube/blob/master/helm/openwhisk/runtimes.json

5. Update wskdeploy with php:7.3

• Update spec, and tests for php:7.3
  https://github.com/apache/incubator-openwhisk-wskdeploy/blob/master/runtimes/runtimes.go#L267
  https://github.com/apache/incubator-openwhisk-wskdeploy/blob/master/specification/html/spec_actions.md#valid-runtime-names
  https://github.com/apache/incubator-openwhisk-wskdeploy/blob/master/tests/src/integration/runtimetests/manifest.yaml#L5

6 Update website with php:7.3

• Update js action section with php:7.3
  https://github.com/apache/incubator-openwhisk-website/blob/master/_layouts/documentation.html
  https://github.com/apache/incubator-openwhisk-website/tree/master/_includes/code

[csantanapr]

@akrabat will be working on this

[akrabat]

All required PRs opened I believe.

[csantanapr]

All PRs have being merged, Thanks ❤️ @akrabat 👍