app: turn the input devices dialog into a session managed toplevel

It works exactly as the keyboard shortcuts dialog now and has its own
menu entry: Edit -> Input Devices.

app/dialogs/dialogs-constructors.c

@@ -77,6 +77,7 @@
 #include "file-open-location-dialog.h"
 #include "file-save-dialog.h"
 #include "image-new-dialog.h"
+#include "input-devices-dialog.h"
 #include "keyboard-shortcuts-dialog.h"
 #include "module-dialog.h"
 #include "palette-import-dialog.h"
@@ -161,6 +162,15 @@ dialogs_keyboard_shortcuts_get (GimpDialogFactory *factory,
   return keyboard_shortcuts_dialog_new (context->gimp);
 }
 
+GtkWidget *
+dialogs_input_devices_get (GimpDialogFactory *factory,
+                           GimpContext       *context,
+                           GimpUIManager     *ui_manager,
+                           gint               view_size)
+{
+  return input_devices_dialog_new (context->gimp);
+}
+
 GtkWidget *
 dialogs_module_get (GimpDialogFactory *factory,
                     GimpContext       *context,