[Victory] For FWD and BWD the user should be able to load models somehow

[Surbhi2111]

The FWD and BWD transformations should start by prompting the user to choose an input model and there shouldn't be a "default" model to start these transformations.

[Ayurshi]

yes makes a lot of sense. Also to add to it, currently saved models with time stamp can't be used as src/trg to run the fwd/bwd transformation, only the models named as src.xmi/trg.xmi can we used.