Validations during add-in packaging: [Script] attribute


During the creation of an installation package of an add-in (invoked by the Create method inside the PackageBuilder class), there is now an extra validation added to check whether all source codes inside the install folder of the add-in have a script attribute.
If one or more source files don't have such an attribute, the building process of the package will be aborted and all source files with the missing script attribute will be printed in the output.