logging: cli options to filter for modules using -v

old style "-v" still works

filtering examples:
-v=debug,network=error,interface=error      // effectively blacklists network and interface
-v=warning,network=debug,interface=debug    // effectively whitelists network and interface

electrum/__init__.py

@@ -1,5 +1,5 @@
 from .version import ELECTRUM_VERSION
-from .util import format_satoshis, set_verbosity
+from .util import format_satoshis
 from .wallet import Wallet
 from .storage import WalletStorage
 from .coinchooser import COIN_CHOOSERS