In Config, name and session_id was quite equal, remove name

session_id is now validate
set_value return Configs with error
add new_config to MetaConfig

tiramisu/option/baseoption.py

@@ -42,7 +42,7 @@ if sys.version_info[0] >= 3:  # pragma: no cover
 
 StorageBase = get_storages_option('base')
 submulti = 2
-name_regexp = re.compile(r'^[a-z][a-zA-Z\d\-_]*$')
+name_regexp = re.compile(r'^[a-z][a-zA-Z\d_]*$')
 forbidden_names = frozenset(['iter_all', 'iter_group', 'find', 'find_first',
                              'make_dict', 'unwrap_from_path', 'read_only',
                              'read_write', 'getowner', 'set_contexts'])