GUAC-587: Allow extensions to be version-independent.

guacamole/src/main/java/org/glyptodon/guacamole/net/basic/extension/ExtensionModule.java

@@ -63,6 +63,7 @@ public class ExtensionModule extends ServletModule {
      */
     private static final List<String> ALLOWED_GUACAMOLE_VERSIONS =
         Collections.unmodifiableList(Arrays.asList(
+            "*",
             "0.9.6"
         ));