Add documentation about Spring and Hibernate

[henri-tremblay]

A lot of users are using Ehcache as

• Second level cache with Hibernate
• Caching implementation for Spring cache

We are currently showing how to do it with Spring-Boot in the Fullstack demo.

But we should also have a dedicated documentation about it.

[linghengqian]

Hey, does EhCache have a more detailed entry level case for springBoot integration?