Make modal pop-ups more obvious by darkening the rest of the screen + allow closing modal by clicking background; improves #62

Prevent mutiple submits of form, when success modal is shown; also show alter (for pretty exceptional case of severe network problem); resolves #62

Move $t['free_text_select'][] from translations.php to config.local.translations.php (since it is library specific)

Make switching between lbs3 and lbs4 version basically just an configuration option without need to adjust form; resolves #59