misc python3 updates:

- use jsonrpclib-pelix
 - update the kivy gui
 - update plugins

gui/kivy/__init__.py

@@ -39,7 +39,6 @@ except ImportError:
 # minimum required version for kivy
 kivy.require('1.8.0')
 from kivy.logger import Logger
-from main_window import ElectrumWindow
 
 
 
@@ -54,6 +53,7 @@ class ElectrumGui:
         self.plugins = plugins
 
     def main(self):
+        from .main_window import ElectrumWindow
         self.config.open_last_wallet()
         w = ElectrumWindow(config=self.config,
                            network=self.network,