Merge pull request #426 from dmitryrogozhny/placeholder-remove-unused-css

Placeholder: remove unused and vendor specific CSS

Author: AJIXuMuK

src/controls/placeholder/PlaceholderComponent.module.scss

@@ -1,14 +1,9 @@
 @import '~office-ui-fabric-react/dist/sass/References.scss';
 
 .placeholder {
-    display: -webkit-box;
-    display: -ms-flexbox;
     display: flex;
 
     .placeholderContainer {
-        -webkit-box-align: center;
-        -ms-flex-align: center;
-        -ms-grid-row-align: center;
         align-items: center;
         color: "[theme:neutralSecondary, default: #666666]";
         background-color: "[theme:neutralLighter, default: #f4f4f4]";
@@ -97,15 +92,3 @@
         }
     }
 }
-
-.placeholderOverlay {
-    position: relative;
-    height: 100%;
-    z-index: 1;
-
-    .placeholderSpinnerContainer {
-        position: relative;
-        width: 100%;
-        margin: 164px 0
-    }
-}