make card info checkable and toggle with menu item / keyboard shortcut

aqt/main.py

@@ -677,7 +677,7 @@ Debug info:\n%s""") % traceback.format_exc(), help="DeckErrors")
         self.moveToState("overview")
 
     def onCardStats(self):
-        self.cardStats.show()
+        self.cardStats.toggle()
 
     def onStats(self):
         aqt.stats.DeckStats(self)

aqt/stats.py

@@ -37,6 +37,13 @@ class CardStats(object):
         if self.shown:
             self.mw.remDockable(self.shown)
             self.shown = None
+            self.mw.form.actionCstats.setChecked(False)
+
+    def toggle(self):
+        if self.shown:
+            self.hide()
+        else:
+            self.show()
 
     def _visChange(self, vis):
         if not vis:

designer/main.ui

@@ -143,6 +143,9 @@
    </property>
   </action>
   <action name="actionCstats">
+   <property name="checkable">
+    <bool>true</bool>
+   </property>
    <property name="text">
     <string>&amp;Card Info</string>
    </property>