Create modified resources package should also be able to create the milestone file

[raducoravu]

We got feedback from one of our end users:

    In addition, we would like the first milestone to be created automatically when 
    we create the first zip package. 
   Yes, the first time I choose “Created modified files package,” besides building the ZIP, 
   Oxygen should also create the first milestone.

So when the user attempts to create a ZIP but they have not yet created the milestone file maybe they could also be prompted if they want to create the milestone file.