Added wrapper_archiver option

To give user a possibility to choose what archiver he can use another
options was introduced for cd32 and archive wrapper modules. This option
will indicate what archiver should be used for compressing the save
state directories.

fs_uae_wrapper/utils.py

@@ -217,3 +217,8 @@ def get_config(conf_file):
         config['_base_dir'] = conf_dir
 
     return config
+
+
+def get_arch_ext(archiver_name):
+    """Return extension for the archiver"""
+    return file_archive.Archivers.get_extension_by_name(archiver_name)