one big commit, sorry

changing looks of input & buttons
changing background color of right panels
moving invite button around
change margins and paddings in memberlist

res/css/structures/_FilePanel.scss

@@ -16,11 +16,8 @@ limitations under the License.
 
 .mx_FilePanel {
     order: 2;
-
     flex: 1 1 0;
-
-    width: 100%;
-
+    background-color: $secondary-accent-color;
     overflow-y: auto;
 }