Base template fix

[simpleigh]

Hi Kaspars,

Thanks so much for your work on Django Suit.

I've spotted a tiny bug in the base.html admin template where the {% block %} / {% endblock %} and <span> / </span> elements don't quite nest correctly - they're currently as follows:

<span class="user-links">
{% block userlinks %}
    <!-- ... -->
  </span>
{% endblock %}

This makes it slightly trickier to override the block as it's harder to avoid creating invalid HTML. First commit fixes; second makes a tiny indentation tweak.

This isn't relevant to your bs3 branch which refactors this area of the template, but should apply cleanly to develop.