Restructure 'screen-hd' CSS rules

Concatenating all `margin-left` rules. This has 0 byte-saving
impact after gzipping at all, it's just about code style.
Also applying coding convention on media query in 'skin.json'.

Change-Id: Ica8557fcd519dea913fe4c30b1be1bfe0d0919c0

screen-hd.less

@@ -2,26 +2,29 @@
 
 @import 'variables.less';
 
-.mw-body {
-	margin-left: 11em;
-	padding: 1.25em 1.5em 1.5em 1.5em;
-}
+.mw-body,
+#mw-head-base,
+#left-navigation,
 #footer {
 	margin-left: 11em;
+}
+
+.mw-body {
+	padding: 1.25em 1.5em 1.5em 1.5em;
+}
+
+#footer {
 	padding: 1.25em;
 }
+
 #mw-panel {
 	padding-left: 0.5em;
 }
+
 #p-search {
 	margin-right: 1em;
 }
-#left-navigation {
-	margin-left: 11em;
-}
+
 #p-personal {
 	right: 1em;
 }
-#mw-head-base {
-	margin-left: 11em;
-}

skin.json

@@ -45,7 +45,7 @@
 					"media": "screen"
 				},
 				"screen-hd.less": {
-					"media": "screen and (min-width: 982px)"
+					"media": "screen and ( min-width: 982px )"
 				},
 				"print.less": {}
 			}