Fix legacy messages (#2323)

* Fix legacy message styling

- Code cleanup;
- Enable constants-mobile;
- Add _legacy-messages.scss;
- Add status color fg colors to theme constants;

* CSS refactoring, significant migration for messages classes

- Many messages classes migrated;
- c-click-icon > c-icon-button;
- c-click-icon rewritten;
- __close-btn refined in dialogs;

* About and splash screen styling

- Fixed splash in About screen;

* Update _mixins.scss

* Convert c-overlay__close-button to button

- <a> -> <button>;
- Set color of button;
- Normalized naming from close-btn to close-button;

* Fixed brightness filter issue on elements in overlays in VISTA;

* Fix dismiss button

platform/commonUI/general/res/templates/message-banner.html

@@ -1,13 +1,13 @@
 <div ng-controller="BannerController" ng-show="active.notification"
-     class="l-message-banner s-message-banner {{active.notification.model.severity}}" ng-class="{
+     class="c-message-banner {{active.notification.model.severity}}" ng-class="{
      'minimized': active.notification.model.minimized,
      'new': !active.notification.model.minimized}"
      ng-click="maximize(active.notification)">
-    <span class="banner-elem label">
+    <span class="c-message-banner__message">
         {{active.notification.model.title}}
     </span>
     <span ng-show="active.notification.model.progress !== undefined || active.notification.model.unknownProgress">
-        <mct-include key="'progress-bar'" class="banner-elem"
+        <mct-include key="'progress-bar'" class="c-message-banner__progress-bar"
                      ng-model="active.notification.model">
         </mct-include>
     </span>
@@ -16,5 +16,5 @@
        ng-click="action(active.notification.model.primaryOption.callback, $event)">
         {{active.notification.model.primaryOption.label}}
     </a>
-    <a class="banner-elem close icon-x" ng-click="dismiss(active.notification, $event)"></a>
+    <button class="c-message-banner__close-button c-click-icon icon-x-in-circle" ng-click="dismiss(active.notification, $event)"></button>
 </div>