Applied fixes due to latest Drupal 8 version.

VisualizationSettingsForm.php - see https://drupal.org/node/2089731
Visualization.php - see https://drupal.org/node/2096117 and https://drupal.org/node/2070823
Visualization.info.yml - see https://drupal.org/node/2107171
Visualization.routing.yml - see https://drupal.org/node/2089727
js/gva.js - see https://drupal.org/node/1793334