Document upload

* adds document upload form
* refactors modal form templates into form classes
* adds document upload route to intervention routes of urls.py

templates/modal/modal_form.html

@@ -5,7 +5,7 @@
 {% endcomment %}
 
 
-<form method="post" action="{{form.action_url}}">
+<form method="post" action="{{form.action_url}}" {% for attr_key, attr_val in form.form_attrs.items %} {{attr_key}}="{{attr_val}}"{% endfor %}>
   {% csrf_token %}
     <div class="modal-header">
         <h5 class="modal-title">{{form.form_title}}</h5>