Provide some means to change the behavior of a single package instance
- New package parameter: PackageInitParameter When set to some value other than empty, the package "init" method (e.g. of xowiki::Package, or one of the subclasses) can handle this separately. - This submit adds a handler for the value "swa-only", and returns a user-friendly message in this case. Of course, we could achieve something similar via permissions as well, but this allows us to tailor the behavior in more details. - In general, this mechanism can also be used to provide some hints about some specific packages, or tailor these in some other ways. - Currently, this new package parameter is not added to the .info file, so configure it via parameter pages.