Updated JavaEBean.md to explain the transactional actions properly

It was written that Ebean won't use transactions, so you needed to use some Ebean features, and thats not true.

A guy called Rob Bygrave writed some stuff(and didn't deleted the wrong stuff) but I think that is not explained properly, so I deleted all the wrong lines and writed a little explanation.
Merge pull request #1381 from BrunoLopezGarcia/patch-1

Updated JavaEBean.md to explain the transactional actions properly