* pr/229:
  Polish contribution
  Put Ehcache back

Closes gh-229

Encapsulation is better that way (and tere is a getter for all of them
anyway).

The fact that it was still there on the classpath means it needs to
be configured (and fails silently if you don't). Removed to give
us some tmie to reconsider.

It's better maintained and it seems to provide more features
as well.

Vet, Owner, Visit. The Visit "aggregate" is a little artificial
but it demonstrates a useful point about not holding on to
references of "parent" (reference data) objects, i.e. the Visit has
an Integer petId, instead of a Pet field. In principle this app is
now almost ready to migrate to multiple services if anyone wanted
to do that.