fixed preview macro with 4:3 thumbnails, closes #146

templates/macros.html

@@ -3,7 +3,7 @@
 	<a href="{{url_for('lecture', id=lecture['id'])}}" title="{{ lecture.course.title }}" style="color: #000">
 		<div class="hidden-xs">
 			<div class="row">
-				<img class="col-xs-4" style="max-height: 100px; width: auto;" src="{{ config.VIDEOPREFIX }}/{{ lecture['titlefile'] }}" alt="Vorschaubild" onerror="this.src='{{url_for('static',filename='no-thumbnail.png')}}'; this.onerror=''; ">
+				<img class="col-xs-4" style="max-height: 120px; height: auto; width:170px" src="{{ config.VIDEOPREFIX }}/{{ lecture['titlefile'] }}" alt="Vorschaubild" onerror="this.src='{{url_for('static',filename='no-thumbnail.png')}}'; this.onerror=''; ">
 				<div class="col-xs-4">
 					<span><strong>{{ lecture.course.short }}</strong>{% if ismod() %} <i>({{lecture.course_id}})</i>{% endif %}</span><br>
 					<span>{% if ismod() %}ID: {{lecture.id}}{% endif %}</span><br>