support aulternative_url's for spatial widget. This allows placing of…

… the widget on pages other then the default dataset page. Use full_current_url to allow for ckan instances that are not hosted at the root, aka in sub folders.

To use:
{% snippet "spatial/snippets/spatial_query.html", default_extent=[[15.62, -139.21], [64.92, -61.87]] alternaive_url=h.full_current_url()%}

ckanext/spatial/templates/spatial/snippets/spatial_query.html

@@ -15,7 +15,7 @@
   <h2 class="module-heading">
     <i class="icon-medium icon-globe"></i>
     {{ _('Filter by location') }}
-    <a href="{{ h.remove_url_param(['ext_bbox','ext_prev_extent', 'ext_location']) }}" class="action">{{ _('Clear') }}</a>
+    <a href="{{ h.remove_url_param(['ext_bbox','ext_prev_extent', 'ext_location'], alternative_url=alternative_url) }}" class="action">{{ _('Clear') }}</a>
   </h2>
   {% set map_config = h.get_common_map_config() %}
   <div class="dataset-map" data-module="spatial-query" data-default_extent="{{ default_extent }}" data-module-map_config="{{ h.dump_json(map_config) }}">