inputs sanitation & remove some obsolete version checks

using filter_vars instead of filter_input, because our unit tests depend on manipulating global arrays, which are not used by filter_input - we would have to mock the function in the unit testing, it therefore is cleaner to use the same code paths in testing as in production

some inputs in I18n and TrafficLimiter remain unfiltered, since we already validate them by other means (IP lib and/or preg_match)

our minimum PHP version is 7.3, so we can drop the two < 5.6 fallback checks

lib/Model/AbstractModel.php

@@ -108,7 +108,7 @@ abstract class AbstractModel
         $this->_data = $data;
 
         // calculate a 64 bit checksum to avoid collisions
-        $this->setId(hash(version_compare(PHP_VERSION, '5.6', '<') ? 'fnv164' : 'fnv1a64', $data['ct']));
+        $this->setId(hash('fnv1a64', $data['ct']));
     }
 
     /**