Log warning when SQL Ops are used in JPQLSerializer

[jwgmeligmeyling]

I see a lot of comments / questions from users that combine querydsl-jpa and querydsl-sql and magically expect SQL operators (like statistical functions or window functions) to "just work" in JPQL, even though standard function support in JPA is very limited. For these to work, users have to register these functions as custom functions in their ORM as well as extend JPATemplates to pass through these functions.

To prevent absolute pollution of Stack Overflow and our issue tracker, I suggest we simply log a warning when the JPQLSerializer traverses an Operation from the com.querydsl.sql package.