Broke out the table column templates into individual template files

templates/tables/columns/users-via_roles.html.twig

@@ -0,0 +1,9 @@
+<script id="{{table.id}}-column-via-roles" type="text/x-handlebars-template">
+    {% verbatim %}
+    <td>
+        {{#each row.roles_via }}
+            <a href="{% endverbatim %}{# Handlebars can't access variables in the global scope, so we have to use Twig to insert the base url #}{{site.uri.public}}{% verbatim %}/roles/r/{{this.slug}}" class="label label-primary" title="{{this.description}}">{{this.name}}</a>
+        {{/each}}
+    </td>
+    {% endverbatim %}
+</script>