Add explicit padding and margins for all ul elements

The lack of such styles causes unwanted spacing on ul elements
that are not within `.mw-content-ltr`, most noticeably on the
watchlist (T181275) and search result pages (T181287).

Bug: T181275
Bug: T181287
Change-Id: I3402c3e297abbbbbcc19d69acee9808195c1f99a

resources/screen-common.less

@@ -399,6 +399,11 @@ p {
 	margin: 0.9em 0 0.8em;
 }
 
+ul {
+	padding: 0;
+	margin: 0.3em 0 0 1.6em;
+}
+
 .center,
 .center * {
 	margin: auto;