Redesign search_form to use bootstrap button addon with icon

based on django_admin_bootstrapped/bootstrap3/templates/admin/search_form.html

sigiStatic/css/base_site.css

@@ -208,3 +208,13 @@ div#footer a {
 h1 {
     margin-bottom: 20px;
 }
+
+.form-group button {
+    /* TODO:
+    consider undoing change done to '.form-group input[type="text"]'
+    in dajngo_admin_bootstraped overrides.css
+    instead of adujsting this */
+
+    height: 28px;
+    padding-top: 4px;
+}

templates/admin/search_form.html

@@ -0,0 +1,25 @@
+{% load i18n admin_static %}
+{% if cl.search_fields %}
+
+<form class="navbar-form navbar-right" role="search" id="changelist-search" action="" method="get">
+
+<div class="form-group"><!-- DIV needed for valid HTML -->
+    <div class="input-group">
+        <input type="text" class="form-control search-query" placeholder="{% trans 'Search' %}" size="40" name="{{ search_var }}" value="{{ cl.query }}" id="searchbar" />
+        <span class="input-group-btn">
+            <button class="btn btn-default" type="submit">
+                <span class="glyphicon glyphicon-search"></span>
+            </button>
+        </span>
+    </div>
+</div>
+
+{% if show_result_count %}
+    <span class="small quiet">{% blocktrans count counter=cl.result_count %}{{ counter }} result{% plural %}{{ counter }} results{% endblocktrans %} (<a href="?{% if cl.is_popup %}pop=1{% endif %}">{% blocktrans with full_result_count=cl.full_result_count %}{{ full_result_count }} total{% endblocktrans %}</a>)</span>
+{% endif %}
+{% for pair in cl.params.items %}
+    {% ifnotequal pair.0 search_var %}<input type="hidden" name="{{ pair.0 }}" value="{{ pair.1 }}"/>{% endifnotequal %}
+{% endfor %}
+</form>
+<script type="text/javascript">document.getElementById("searchbar").focus();</script>
+{% endif %}