Add templates for timetable. Advances #1.

biscuit/apps/chronos/templates/chronos/tt_lesson.html

@@ -7,12 +7,12 @@
   </div>
   <div class="row">
    <div class="col-sm">
-    {% for group in lesson_period.lesosn.groups %}
+    {% for group in lesson_period.lesson.groups.all %}
      <span class="card-text">{{ group.short_name }}</span>
     {% endfor %}
    </div>
    <div class="col-sm">
-    {% for teacher in lesson_period.lesosn.teachers %}
+    {% for teacher in lesson_period.lesson.teachers.all %}
      <span class="card-text">{{ teacher.short_name }}</span>
     {% endfor %}
    </div>