Improve doc for GlobalCRUDSettings

Now describe two ways to initialize the play application launcher : directly or by creating your own class extending GlobalCRUDSettings.
Correct one typo

Alternatively, `play.utils.dao.CachedDAO` cn be used to cache fetched data. ->
Alternatively, `play.utils.dao.CachedDAO` can be used to cache fetched data.
Improve doc for Custom DAO

Add global definition and override function examples. The inject annotation was required for my constructor to work, but I don't know if it is the case for everyone.
Reference to the class SampleDAO

If an user just read this documentation page, he doesn't know what the class SampleDAO is. He may think this is a build-in class in the play2-crud framework. The reference help him getting it right.
Add inject requirement

The inject annotation associated with the CRUDController constructor was required for my constructor to work. I don't know if it the case for everyone. That kind of information could have saved me a lot of time.
Doc for the CRUDController function overriding
Merge pull request #45 from gbersac/master

Improving documentation