Allow Zipping XED files

Some XED files can be pretty big, for example the solr-core one is almost 500kB (mostly because of a huge number of managed dependencies) and XWiki Standard 14.0 WAR contains a total of 40MB of XED files.

Zipping those would reduce a lot their weight, since they are XML files with a lot of repeated elements. For example, the 500kB solr-core becomes a 16kB zip file.