Nmld collections jvstm backend merge

Refactoring of the code generation with regard to relations "to-many". It is now possible to define which DML-designed-collection is meant to be used by the code generation performed by the backends. The parametrization that overrides the default of each backend may be performed in the pom.xml of the application using the <params> tag and the <collectionClassName> tag.

There is also a new backend available, which provides only transactional management and lacks persistence --- it uses the JVSTM to do so. At this point the dependency is still towards the JVSTM used in the Fénix instantiation at CIIST/DSI.