Link from topic thread to the "edit topic" page

Also, "Edit topics" button renamed to "Topics", so that it does not
get confused with "Edit topic".

templates/course.html

@@ -7,7 +7,7 @@
 
 	{% if g.is_teacher %}
 		<div class=buttons>
-			<a class=button href='{{ url_for('admin_topics', sident=g.course.sident, cident=g.course.ident) }}'>Edit topics</a>
+			<a class=button href='{{ url_for('admin_topics', sident=g.course.sident, cident=g.course.ident) }}'>Topics</a>
 			<a class=button href='{{ url_for('teacher', sident=g.course.sident, cident=g.course.ident) }}'>Teacher's summary</a>
 			<a class=button href='{{ url_for('admin_course', sident=g.course.sident, cident=g.course.ident) }}'>Details</a>
 		</div>

templates/topic.html

@@ -10,6 +10,7 @@
 	<div class="buttons">
 		<a class="button" href='{{ url_for('course_index', sident=g.course.sident, cident=g.course.ident) }}'>Back to the course</a>
 	{% if g.is_teacher %}
+		<a class="button" href='{{ url_for('admin_topics', sident=g.course.sident, cident=g.course.ident) }}'>Topics</a>
 		<a class="button" href='{{ url_for('teacher', sident=g.course.sident, cident=g.course.ident) }}'>Teacher's summary</a>
 		<a class="button" href='{{ url_for('admin_edit_topic', sident=g.course.sident, cident=g.course.ident, tid=g.topic.tid) }}'>Edit topic</a>
 	{% elif g.is_grader %}