(mvc/template) add heading support, proposal for https://github.com/opnsense/core/pull/866

Example (from @fraenki):
<field>
        <label>Tuning Options</label>
        <type>header</type>
</field>

src/opnsense/mvc/app/views/layout_partials/base_dialog.volt

@@ -34,6 +34,27 @@ label           :   dialog label
 
 #}
 
+{# close table and reopen for new header#}
+{%- macro base_dialog_header(header_text) %}
+      </tbody>
+    </table>
+  </div>
+  <div class="table-responsive">
+    <table class="table table-striped table-condensed">
+        <colgroup>
+            <col class="col-md-3"/>
+            <col class="col-md-{{ 12-3-msgzone_width|default(5) }}"/>
+            <col class="col-md-{{ msgzone_width|default(5) }}"/>
+        </colgroup>
+        <thead>
+          <tr colspan="3">
+            <th><h2>{{header_text}}</h2></th>
+          </tr>
+        </thead>
+        <tbody>
+{%- endmacro %}
+
+
 
 {# Find if there are help supported or advanced field on this page #}
 {% set help=false %}
@@ -61,7 +82,8 @@ label           :   dialog label
             </div>
             <div class="modal-body">
                 <form id="frm_{{id}}">
-                    <table class="table table-striped table-condensed table-responsive">
+                  <div class="table-responsive">
+                    <table class="table table-striped table-condensed">
                         <colgroup>
                             <col class="col-md-3"/>
                             <col class="col-md-{{ 12-3-msgzone_width|default(5) }}"/>
@@ -77,10 +99,16 @@ label           :   dialog label
                         </tr>
                         {% endif %}
                         {% for field in fields|default({})%}
-                            {{ partial("layout_partials/form_input_tr",field)}}
+                            {% if field['type'] == 'header' %}
+                              {# close table and start new one with header #}
+                              {{ base_dialog_header(field['label']) }}
+                            {% else %}
+                              {{ partial("layout_partials/form_input_tr",field)}}
+                            {% endif %}
                         {% endfor %}
                         </tbody>
                     </table>
+                  </div>
                 </form>
             </div>
             <div class="modal-footer">

src/opnsense/mvc/app/views/layout_partials/base_form.volt

@@ -34,6 +34,25 @@ data_title      :   data-title to set on form
 
 #}
 
+{# close table and reopen for new header#}
+{%- macro base_form_header(header_text) %}
+      </tbody>
+    </table>
+  </div>
+  <div class="table-responsive">
+    <table class="table table-striped table-condensed table-responsive">
+        <colgroup>
+            <col class="col-md-3"/>
+            <col class="col-md-4"/>
+            <col class="col-md-5"/>
+        </colgroup>
+        <thead>
+          <tr colspan="3">
+            <th><h2>{{header_text}}</h2></th>
+          </tr>
+        </thead>
+        <tbody>
+{%- endmacro %}
 
 {# Find if there are help supported or advanced field on this page #}
 {% set help=false %}
@@ -52,7 +71,8 @@ data_title      :   data-title to set on form
 {%     endif %}
 {% endfor %}
 <form id="{{id}}" class="form-inline" data-title="{{data_title|default('')}}">
-    <table class="table table-striped table-condensed table-responsive">
+  <div class="table-responsive">
+    <table class="table table-striped table-condensed">
         <colgroup>
             <col class="col-md-3"/>
             <col class="col-md-4"/>
@@ -66,7 +86,12 @@ data_title      :   data-title to set on form
             </td>
         </tr>
         {% for field in fields|default({})%}
-            {{ partial("layout_partials/form_input_tr",field)}}
+            {% if field['type'] == 'header' %}
+              {# close table and start new one with header #}
+              {{ base_form_header(field['label']) }}
+            {% else %}
+              {{ partial("layout_partials/form_input_tr",field)}}
+            {% endif %}
         {% endfor %}
         {% if apply_btn_id|default('') != '' %}
         <tr>
@@ -75,4 +100,5 @@ data_title      :   data-title to set on form
         {% endif %}
         </tbody>
     </table>
+  </div>
 </form>