Add support for displayName to profiles, so that ugly user IDs on sites like Stack Exchange can be hidden

config/models

@@ -22,6 +22,7 @@ Profile
     userId UserId
     siteId SiteId
     username Text sqltype=varchar(255)
+    displayName Text Maybe sqltype=varchar(255)
 
 Entry
     slug Slug

templates/mf2/h-card.hamlet

@@ -22,4 +22,7 @@
         <li>
           <a .u-url itemprop="sameAs" rel="me" href="#{substitute template profile}">
             <i .fa.fa-#{siteIcon site}>
-            #{profileUsername profile}
+            $maybe name <- profileDisplayName profile
+              #{name}
+            $nothing
+              #{profileUsername profile}