forum posts, comments: make timestamps into permalinks.

Make the timestamp beneath the username on forum posts into a permalink
that links to the post in full context of the thread. For comments, make
the timestamp link to the comment in full context of the post.

* Make the timestamp in forum posts link to /forum_posts/123.
* Make the timestamp in comments link to /posts/456#comment_123.
* Make /forum_posts/123 redirect to /forum_topics/456#forum_post_123.
* Make /comments/123 redirect to /posts/456#comment_123.
* Remove the "ID: ###" and "Permalink" fields from forum posts.

app/views/comments/partials/show/_comment.html.erb

@@ -1,6 +1,6 @@
 <% if CurrentUser.is_moderator? || (params[:search] && params[:search][:is_deleted] =~ /t/) || !comment.is_deleted? %>
   <a name="comment-<%= comment.id %>"></a>
-  <article class="comment message"
+  <article id="comment_<%= comment.id %>" class="comment message"
            data-id="<%= comment.id %>"
            data-post-id="<%= comment.post_id %>"
            data-creator-id="<%= comment.creator_id %>"
@@ -18,7 +18,7 @@
           (deleted)
         <% end %>
       </h4>
-      <%= time_ago_in_words_tagged(comment.created_at) %>
+      <%= link_to time_ago_in_words_tagged(comment.created_at), post_path(comment.post, anchor: "comment_#{comment.id}"), class: "message-timestamp" %>
     </div>
     <div class="content">
       <div class="body prose">