connection query without content is now possible

[manuel-mauky]

Fix for #14 With this fix you can write a queries like:

{
    HumanConnection(paginationRequest: { page: 1, size: 2}) {
        totalPages
        totalElements
    }
}

This can be useful if you are only interested in the number of elements and pages but don't need any content.

The implementation uses the fact that in the criteria query a list of Predicate is created based on Field.getAttributes(). I'm passing an empty Field which results in an empty predicate list.