Delay loading modules and objects until gettext is loaded

This was resulting in strings not getting translated, especially when
the calls to gettext came at the lowest indent level of the module.

zenmap/zenmapGUI/App.py

@@ -163,8 +163,6 @@ import zenmapCore.I18N
 from zenmapCore.Paths import Path
 from zenmapCore.Name import APP_DISPLAY_NAME
 
-from zenmapGUI.MainWindow import ScanWindow
-
 from zenmapGUI.higwidgets.higdialogs import HIGAlertDialog
 
 # A global list of open scan windows. When the last one is destroyed, we call
@@ -186,6 +184,7 @@ def _destroy_callback(window):
 
 
 def new_window():
+    from zenmapGUI.MainWindow import ScanWindow
     w = ScanWindow()
     w.connect("destroy", _destroy_callback)
     if is_maemo():