Tidy up websocket starter

Fixes gh-396
Add howto for Jetty
Explicitly manager javassist version

Hibernate is picky about javassist, but unfortunately that
library is used by other parts of our stack (Thymeleaf!?), so
we need a policy for resolving the dependency transitively.
I fixed it to the version in Hibernate 4.3.1 (our current
best foot forward), but it will have to be updateed whenever
Hibernate is.

Fixes gh-402
Make Spring Boot tests locale independent

Fixes gh-405
Add @Configuration to WebMvcAutoConfigurationAdapter
Expose setter for Map store in InMemoryMetricRepository

User can then use a weak reference map (for instance), if worried
about memory usage.
Spring Data Rest Starter Project

Fixes gh-60
Add spring-data-rest sample
Be defensive if there is no main/classes
Add docs for starter pom usage
Hacking