DATAJPA-516 - Improve error logging for missing referenced named query methods.

We now a debug message in CreateIfNotFoundQueryLookupStrategy if we fail to resolve a query method with the @Query.name property set explicitly. 
Unfortunately we cannot fail fast here, since a user could define the following Repository:
```java
interface UserRepository extends JpaRepository<User,Long>{
   @Query(name="customizable_query_123")
   List<User> findUserByNameLike(String name);
}
```
The named query "customizable_query_123" could be an empty externally predefined hook to override the default behaviour of the findUserByNameLike() query method, if necessary.

Original pull request: #83.