added basic mobile styles to extension manager (not great, but makes things at least readable)

lib/plugins/extension/all.less

+
+@media only screen and (max-width: 600px) {
+
+#extension__list .legend {
+    > div {
+        padding-left: 0;
+    }
+
+    div.screenshot {
+        margin: 0 .5em .5em 0;
+    }
+
+    h2 {
+        width: auto;
+        float: none;
+    }
+
+    div.linkbar {
+        clear: left;
+    }
+}
+
+} /* /@media */