qml: don't initialize instance variables on class scope for non-singletons

(this somehow escaped attention before, as most objects usually don't have multiple instances,
unless multiple wallets are open at the same time.)
Also, move all signal declarations, class constants and variables to the top of class definitions.

electrum/gui/qml/qenetwork.py

@@ -8,17 +8,6 @@ from .util import QtEventListener, event_listener
 from .qeserverlistmodel import QEServerListModel
 
 class QENetwork(QObject, QtEventListener):
-    def __init__(self, network, qeconfig, parent=None):
-        super().__init__(parent)
-        self.network = network
-        self._qeconfig = qeconfig
-        self._serverListModel = None
-        self._height = network.get_local_height() # init here, update event can take a while
-        self.register_callbacks()
-
-        self._qeconfig.useGossipChanged.connect(self.on_gossip_setting_changed)
-
-
     _logger = get_logger(__name__)
 
     networkUpdated = pyqtSignal()
@@ -47,6 +36,16 @@ class QENetwork(QObject, QtEventListener):
     _gossipDbChannels = 0
     _gossipDbPolicies = 0
 
+    def __init__(self, network, qeconfig, parent=None):
+        super().__init__(parent)
+        self.network = network
+        self._qeconfig = qeconfig
+        self._serverListModel = None
+        self._height = network.get_local_height() # init here, update event can take a while
+        self.register_callbacks()
+
+        self._qeconfig.useGossipChanged.connect(self.on_gossip_setting_changed)
+
     @event_listener
     def on_event_network_updated(self, *args):
         self.networkUpdated.emit()