config: no longer singleton. it is passed to Wallet.__init__

The few other cases that used SimpleConfig.get_instance() now
either get passed a config instance, or they try to get a reference
to something else that has a reference to a config.
(see lnsweep, qt/qrcodewidget, qt/qrtextedit)

electrum/gui/stdio.py

@@ -39,7 +39,7 @@ class ElectrumGui:
         self.str_amount = ""
         self.str_fee = ""
 
-        self.wallet = Wallet(storage)
+        self.wallet = Wallet(storage, config=config)
         self.wallet.start_network(self.network)
         self.contacts = self.wallet.contacts