Redesign extended information page (#4322)

* Redesign extended information page

* Remove unused keys

* Add $ui-base-lighter-color variable to SCSS

app/views/about/_contact.html.haml

@@ -1,5 +1,8 @@
 .panel
-  .panel-header= t 'about.contact'
+  .panel-header
+    = succeed ':' do
+      = t 'about.contact'
+    %span{ title: contact.site_contact_email.presence }= contact.site_contact_email.presence
   .panel-body
     - if contact.contact_account
       .owner
@@ -8,8 +11,9 @@
           = link_to TagManager.instance.url_for(contact.contact_account) do
             %span.display_name.emojify= display_name(contact.contact_account)
             %span.username @#{contact.contact_account.acct}
-
-    - unless contact.site_contact_email.blank?
-      .contact-email
-        = t 'about.business_email'
-        %strong= contact.site_contact_email
+    - else
+      .owner
+        .avatar= image_tag full_asset_url('avatars/original/missing.png')
+        .name
+          %span.display_name= t 'about.contact_missing'
+          %span.username= t 'about.contact_unavailable'