Create a plugin point in CsarUtils to enable customization of the structure of the generated csar on a per model basis.

The concept is similar to the already existing plugin point that enables customization of entries in the csar by implementing CsarEntryGenerator (see CsarUtils populateZip) except the new plugin point shall be for generating the csar itself rather than entries in the csar.

The existing code for generating the csar shall be moved to a new class that shall be the default implementation of the plugin interface