Add cv_gtk3 package.

cv_gtk3/signal_handlers/handlers.py

@@ -0,0 +1,10 @@
+class Handlers:
+    """
+    Class containing all signal handlers for the GTK GUI
+    """
+    def __init__(self, app):
+        """
+        Initialize handler class
+        :param app: reference to an CardvaultGTK object
+        """
+        self.app = app