inital commit for signup

added a basic app using the UserCreationForm to create new user at /accounts/signup/
change outside of the app are:
-added signup to INSTALLED_APPS in /photo21/settings.py
-added accounts/signup/ to path in /photo21/urls.py

should extend UserCreationForm to have field for email and maybe first/last names, except if we want the user to add that themselves later

signup/templates/signup.html

@@ -0,0 +1,9 @@
+{% extends "base.html" %}
+{% block content %}
+<h1>Création d'utilisateur</h1>
+<form action = '' method="post">{% csrf_token %}
+    {{ form }}
+    <br>
+    <input type="submit" value="Envoyer">
+</form>
+{% endblock %}