Readded start>end checking. Template improvements

Added descritpions of all error for the user as well as the image.

Added contextual alert boxes for messages in base.

If  start>end start<=>end. Very simple fix, thanks Charlie.

templates/400.html

@@ -4,6 +4,7 @@
 
 {% block content %}
     <div class="text-center">
+        <h1>400: Bad Request</h1>
         <img src="{% static 'imgs/400.jpg' %}"/>
     </div>
 {% endblock %}