access to global configuration using set_config and get_config

lib/__init__.py

@@ -5,7 +5,7 @@ from wallet import Wallet, Wallet_2of2, Wallet_2of3, Imported_Wallet
 from verifier import TxVerifier
 from network import Network, DEFAULT_SERVERS, DEFAULT_PORTS, pick_random_server
 from interface import Interface
-from simple_config import SimpleConfig
+from simple_config import SimpleConfig, get_config, set_config
 import bitcoin
 import account
 import transaction