Add demo project to the main repository

What we need is to create a project similar to the one in https://github.com/hibernate/hibernate-demos/tree/master/hibernate-ogm/nosql-with-hibernate-ogm-101/hibernate-ogm-demo-nosql-with-hibernate-ogm-101-part-3 but that we run regularly with the integration tests.

THe idea is to have a complete up-to-date example to show users. I've added a link to the forum topic with a user explaining some of the problem that he had trying to running an example I provided. It should give some context and ideas on what we need to highlight.

We probably need to develop this thinking about the fact that it should be tested on different containers, For example, different versions of WildFly or Tomcat. We don't have to do it in the same issue but it would be nice plan for it.

The reason for this issue is that I think it will make it easier to keep the example up to date if we include it in the main project instead of creating a separate repository for it. We might also include it in `hibernate-demos` when we have a version we are happy with.