Switch to REM API for explore WG page

Signed-off-by: Zhou Fang zhou.fang@eclipse-foundation.org

For eclipsefdn/it/websites/membership.eclipse.org#346 (closed)

Need an update from REM API to be able to fetch all wgs (including those we don't want to display on online application form atm, such as openhw and openhw europe)

Can be previewed here:

https://deploy-preview-315--eclipsefdn-solstice-assets.netlify.app/explore-wg.html

And here:

https://staging.eclipse.org/org/workinggroups/explore.php

js/solstice/templates/working-group-list.mustache

+{{#shouldShowFilterOptions.all}}
+<div class="background-mid-grey margin-bottom-30 margin-top-40">
+  <div class="dropdown">
+    <button class="btn btn-secondary dropdown-toggle" type="button" data-toggle="dropdown">Filter Working Groups
+    <span class="caret"></span></button>
+    <ul class="dropdown-menu wg-links">
+      <li><a style="width:150px;" class="wg-btn" data-wg="wg-all-item" role="button">All</a></li>
+      {{#shouldShowFilterOptions.active}}
+        <li><a style="width:150px;" class="wg-btn" data-wg="wg-active-item" role="button">Active</a></li>
+      {{/shouldShowFilterOptions.active}}
+      {{#shouldShowFilterOptions.incubating}}
+      <li><a style="width:150px;" class="wg-btn" data-wg="wg-incubating-item" role="button">Incubating</a></li>
+      {{/shouldShowFilterOptions.incubating}}
+      {{#shouldShowFilterOptions.proposed}}
+      <li><a style="width:150px;" class="wg-btn" data-wg="wg-proposed-item" role="button">Proposed</a></li>
+      {{/shouldShowFilterOptions.proposed}}
+    </ul>
+  </div>
+</div>
+{{/shouldShowFilterOptions.all}}
+
 <div class="row display-flex flex-wrap">
 {{#sections}}
 {{#checkStatus}}