Added support for failsafe TAB

Made in cooperation with skaman82.

Summary of modifications:
- Extended data storage to hold data for new/changed MSP messages.
- Added support for added/changed MSP messages.
- Added assigned mode(s) to AUX labels.
- Tooltip changes.
- Included style modifications to configuration tab from Skaman82.
- Moved all texts from failsafe tab .html to `messages.json`.
- Removed failsafe settings from configuration tab (now obsolete).
- Added failsafe-tab variables to Backup & Restore.
- Reorganized stage 2 elements, cleanup and corrections.

js/gui.js

@@ -18,6 +18,7 @@ var GUI_control = function () {
         'help'
     ];
     this.defaultAllowedTabsWhenConnected = [
+        'failsafe',
         'adjustments',
         'auxiliary',
         'cli',