Use H1 for page title and H2 for tiddler titles

Ideally, we’d also rebase the headings within tiddlers so that `!
Heading` would be an H3. Hopefully we’ll do that later.

core/ui/PageTemplate/sidebar.tid

@@ -7,11 +7,11 @@ tags: $:/tags/PageTemplate
 
 <$reveal state="$:/state/sidebar" type="match" text="yes" default="yes" retain="yes">
 
-<div class="tw-site-title">
+<h1 class="tw-site-title">
 
 <$transclude tiddler="$:/SiteTitle" mode="inline"/>
 
-</div>
+</h1>
 
 <div class="tw-site-subtitle">
 

core/ui/ViewTemplate/title.tid

@@ -5,7 +5,7 @@ tags: $:/tags/ViewTemplate
 fill:$(foregroundColor)$;
 \end
 <div class="tw-tiddler-title">
-<h1 class="titlebar">
+<h2 class="titlebar">
 <span class="tw-tiddler-controls">
 <$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>
-</h1>
+</h2>
 
 <$reveal type="nomatch" text="" default="" state=<<tiddlerInfoState>> class="tw-tiddler-info tw-popup" animate="yes" retain="yes">