ATL Ouput patterns enhancement

A miss in the ATL syntax has just been corrected: the in keyword is now available for both input and output patterns. This enhancement will be available in ATL 3.1.It mainly allow to specify in which model you want to create elements, when the old semantics forbade the use of several output models conforming to the same metamodel declaration. The workaround wasn't very intuitive as it consists on declaring the same metamodel with different names...The use of this keyword is described at the end of this section.