Migrate app to use WTForms for auth form validation

- Not finished yet, major styling breakage in this commit
- Also encapsulated GET & POST requests of /login and /signup routes into one route.

templates/macros.html

@@ -1,12 +1,14 @@
 {% macro render_field(field) %}
-  <dt>{{ field.label }}
-  <dd>{{ field(**kwargs)|safe }}
-  {% if field.errors %}
-    <ul class=errors>
-    {% for error in field.errors %}
-      <li>{{ error }}</li>
-    {% endfor %}
-    </ul>
-  {% endif %}
-  </dd>
+    <field>
+        <label>{{ field.label }}</label>
+        {{ field(**kwargs)|safe }}
+        {% if field.errors %}
+            <ul class=errors>
+                {% for error in field.errors %}
+                    <li>{{ error }}</li>
+                {% endfor %}
+            </ul>
+        {% endif %}
+        <br>
+    </field>
 {% endmacro %}