Upgrade to Ehcache 3 and Java config

I saw on twitter the reference of an article (in french):
http://javaetmoi.com/2016/08/migrer-vers-spring-boot/

That article concludes with something along the lines of  "Besides the
EhCache and Maven configuration, Petclinic does not hold a single line
of XML anymore".

Looking at the code, we can remove more XML if you want. This PR migrates
the cache infrastructure to EhCache 3 and JCache (JSR-107). This also
reduces the number of dependencies.

Conflicts:
	pom.xml
	readme.md
	src/main/java/org/springframework/samples/petclinic/repository/jdbc/JdbcPetRepositoryImpl.java
	src/main/java/org/springframework/samples/petclinic/web/VetController.java
	src/test/java/org/springframework/samples/petclinic/web/CrashControllerTests.java
	src/test/java/org/springframework/samples/petclinic/web/OwnerControllerTests.java
	src/test/java/org/springframework/samples/petclinic/web/PetControllerTests.java
	src/test/java/org/springframework/samples/petclinic/web/VetControllerTests.java
	src/test/java/org/springframework/samples/petclinic/web/VisitControllerTests.java

Merging AbstractClinicServiceTests and ClinicServiceSpringDataJpaTests then using the Spring Boot @DataJpaTest annotation

responsive menu fix - data-target attribute added

Responsive menu fix

Use build finalName instead of warName in pom.xml

responsive menu fix - data-target attribute added

Merge pull request #169 from aaguilera/springboot

This reverts commit be048ae2.

Fix  #157 Upgrade Spring IO Platform to 2.0.5

Migrate to webjars for frontend resource management

- petclinic.css is now auto generated, therefore it is put in the
ignore list
- vendor folder is removed in favour of webjars
- remove several maven dependencies which are already managed by spring
boot
- unfortunately, lesscss maven plugin does NOT support importing from
classpath, as a result, bootstrap is unpacked during process-resources
phase, we need need to find a better resolution
- remove bower integration

Simplify content negotiation setup for vets