Improve the import of other qface files

[Gagi2k]

When importing another qface module, it is expected that this module is also parsed as part of FileSystem.parse(). If that's not the case, no error is reported, but instead the types can't be resolved in the templates.

If all the qface files are parsed, it would make sense to still be able to select which modules should be autogenerated and which modules are just needed to resolve the type simulation. This would make the system more flexible, as the user can define the structure of a big project and generate the modules one by one instead of doing it in one go.

[Gagi2k]

In addition it would be great if we could access the imported module directly from the domain model. Instead the the imports property just provides the import statement.