Update parent pom.xml to setup using GoogleAppEngine

- Add Appengine Maven Plugin
- Add profile to set deployment-specific properties in war-modules' descriptors from .properties file in modules' roots
Update web-client module for GoogleAppEngine

- Add GAE-specific deployment descriptor
- Add welcome-file to web.xml
- Add index.xhtml to test deployment
Update web-service module for Google App Engine

- Add GAE-specific deployment descriptor
- Add welcome-file to web.xml
- Add index.xhtml to test deployment
Add to README paragraph on how to set up deployment