Fix floaring header gradient in FF and settings images

No issue

- Corrects the syntax used for the floating header gradient so it now gets prefixed correctly for Firefox
- Removes padding from `<button>` elements (fixes padding around images in buttons)
- Adds display: block; to settings images to prevent a Webkit bug which adds space under the image

core/client/assets/sass/layouts/settings.scss

@@ -145,6 +145,7 @@
     .settings-general img {
         max-width: 100%;
         max-height: 400px;
+        display: block;
     }
 
     .content {

core/client/assets/sass/patterns/_shame.scss

@@ -45,7 +45,7 @@
     text-transform: uppercase;
     color: $brown;
     //Transparent gradient to make bg fade out as it goes out the top.
-    background: linear-gradient(top, white 0%, white 25%, rgba(255,255,255,0.9) 100%);
+    background: linear-gradient(to bottom, white 0%, white 25%, rgba(255,255,255,0.9) 100%);
 
     // button,
     .button {

core/client/assets/sass/patterns/global.scss

@@ -218,6 +218,7 @@ button {
     border: none;
     outline: none;
     box-shadow: none;
+    padding: 0;
 }