Fix DD4hep build

By fixing an include and fixing the definitions of Grammars. On this second point, DD4hep needs 2 things :

• default constructor for all classes used as conditions
• definition of a Grammar, which can be easily done by including GrammarUnparsed.h In both cases, this is unacceptable constraints on the user code, with no good reasons, but that's how DD4hep is done right now