Introduce jquery formvalidator for com_config ::frontend

#### Executive summary

This PR converts the form validation on com_config to use plain jquery (no mootools call on every form 😄).
Also NO MORE INLINE SCRIPTS!

#### Testing

1. Apply first PR #4888 (!important)
2. Apply this PR
3. In admin menus create a new menu for Configuration Manager -> Display Site Configuration Options 
4. In admin menus create a new menu for Configuration Manager -> Display Template Options
5. Login as administrator in front end
6. Try the new menus, try saving the forms


If no javascript errors are logged in your browser and the functionality remains the same your test is a pass in any other case please report the errors here