Add events for bookmarks and subscribed topics in UCP

We have a PHP event in the UCP (ucp_main_topiclist_topic_modify_template_vars) that allows you to modify template vars, but there's no corresponding events in the template files. I'm proposing two, based on a similar template var in the search_results_body.html file. Preferably fixed in 3.3.8 so I can finish an extension for a client.

ucp_main_bookmarks_topic_title_after

After the <br /> (currently line 56) in ucp_main_bookmarks.html

ucp_main_subscribed_topic_title_after

 After the <br /> (currently line 99) in ucp_main_subscribed.html