Handle submetamodels with inheritance

[NicolasAnquetil]

if we have 2 meta-models mm1 and mm2, mm1 is sub-meta-model of mm2 (ie. mm2 uses entities of mm1).

there is an mm1Entity and an mm2Entity and they don't inherit one from the other

If both generators are based on FamixBasicInfrastructureGenerator, then there are also two SourcedEntity, NamedEntity, Comment, ...

when we translate that to Java, we have "incompatible types", eg two NamedEntity.java that are equals but in separate packages and incompatible ...