Make all WM elements inherit from common templates

core/templates/wm/modal.html

@@ -0,0 +1,19 @@
+{% load static %}
+
+<script src="{% static 'modal.js' %}"></script>
+{% block scripts %}
+{% endblock %}
+
+{% block styles %}
+{% endblock %}
+
+<div id="modal" class="modal is-active is-clipped">
+  <div class="modal-background"></div>
+  <div class="modal-content">
+    <div class="box">
+      {% block modal_content %}
+      {% endblock %}
+      <button class="modal-close is-large" aria-label="close"></button>
+    </div>
+  </div>
+</div>