Rework POM structure

Rework main build POM to be an aggregator pom that does not inherit
from any parent. Introduce new spring-boot-dependencies module to
act as a parent for both spring-boot-starter-parent and
spring-boot-parent.
Fixup sample links in README.md
Cleanups Spring Data JPA example.

Various cleanups to the Spring Data JPA example, including:

* Move repositories into service package and make them package private
  thus only expose the service interfaces to clients.
* Merge HotelRepository and HotelSummaryRepository and make service
  implementations package protected.
* Introduce integration test base class to bootstrap the app as
  SpringAppliation.run would.
* Refactor central test case to rather use Spring MVC integration
  testing framework.
* Add integration tests for repositories to execute query methods.
Merge pull request #9 from olivergierke/master

# By Oliver Gierke
* pull9:
  Cleanups Spring Data JPA example.
Fix problem locating spring home
Correct directory permissions in dist zip
Fix a few problems with spring start script

Fixed a few issues with the spring start script, mainly around symlinks.
Test on OSX, Ubuntu and Windows (Cygwin) with and would symlinks.
Polish and simplify spring bash script
Add spring.bat start script for Windows
Try to debug the travis build
Fix up some links in README
Fix travis build
Accept SPRING_HOME if already set
Remove hardcoded version in Banner
Reinstate junit dependencies in starters
Attempt to sort out logging dependencies
Indicate downloading dependencies progress in CLI

Update CLI to show a "Downloading Dependencies..." message if the
initial dependency resolution takes more than 3 seconds. Whilst
downloading dots are appended to the message.

Issue: #54589094
Add logging initializer to tests
Add websocket starter
Add websocket sample