Add option compatibility

[Jelte Lagendijk]

<file path="WidgetName/widget/" />

is unnecessary in package.xml for Mendix 6, removing it will solve a couple of problems when zipping the src folder with Windows zip. Unfortunately, this will break backwards compatibility with Mendix 5. So we might ask the user for compatibility (whether or not it needs to work in 5 as well) and based on that edit the package.xml file