Fix: Add Parsing of .xml files in ZIP archives

CityDoctorParent/CityDoctorModel/src/main/java/de/hft/stuttgart/citydoctor2/zip/CityGmlZipArchive.java

@@ -39,7 +39,7 @@ public class CityGmlZipArchive implements Serializable {
                 if (ze.isDirectory()) {
                     continue;
                 }
-                if (ze.getName().endsWith(".gml")) {
+                if (ze.getName().endsWith(".gml") || ze.getName().endsWith(".xml")) {
                     archiveEntries.add(CityGmlZipEntry.register(ze, cgmlArchive));
                 }
             }