Use H1 for tiddler titles

Part of #650

core/ui/ViewTemplate/title.tid

@@ -5,7 +5,7 @@ tags: $:/tags/ViewTemplate
 fill:$(foregroundColor)$;
 \end
 <div class="tw-tiddler-title">
-<div class="titlebar">
+<h1 class="titlebar">
 <span class="tw-tiddler-controls">
 <$list filter="[all[shadows+tiddlers]tag[$:/tags/ViewToolbar]!has[draft.of]]" variable="listItem"><$transclude tiddler=<<listItem>>/></$list>
 </span>
@@ -24,7 +24,7 @@ fill:$(foregroundColor)$;
 <$view field="title"/>
 </span>
 </$list>
-</div>
+</h1>
 
 <$reveal type="nomatch" text="" default="" state=<<tiddlerInfoState>> class="tw-tiddler-info tw-popup" animate="yes" retain="yes">
 

themes/tiddlywiki/vanilla/base.tid

@@ -570,6 +570,7 @@ a.tw-tiddlylink-external:hover {
 	font-size: 2.35em;
 	line-height: 1.2em;
 	color: <<colour tiddler-title-foreground>>;
+	margin: 0;
 }
 
 .tw-system-title-prefix {