Fix controls' heights that are displayed in CPPredicateEditor

Lastly, we removed the usage of max-size to enable some controls like CPTextField to have
a specific height. This may caused a CPTextField to have a wrong height.
As all controls in a CPPredicateEditor have a CPControlSize to small, we now force their height to the minimum size.
Merge pull request #2277 from t00f/cppredicate_editor

Fix controls' heights that are displayed in CPPredicateEditor