fix(requests): rework handling of requests

This commit changes several things about how we were handling
package requests.

Modifications (requests):
-------------
- `/requests/{id}/close` no longer provides an Accepted selection.
  All manual request closures will cause a rejection.
- Relevent `pkgbase` actions now trigger request closures:
  `/pkgbase/{name}/delete` (deletion), `/pkgbase/{name}/merge` (merge)
  and `/pkgbase/{name}/disown` (orphan).
- Comment fields have been added to
  `/pkgbase/{name}/{delete,merge,disown}`, which is used to set the
  `PackageRequest.ClosureComment` on pending requests. If the comment
  field is left blank, a closure comment is autogenerated.
- Autogenerated request notifications are only sent out once
  as a closure notification.
- Some markup has been fixed.

Modifications (disown/orphan):
-----------------------------
- Orphan requests are now handled through the same path as
  deletion/merge.
- We now check for due date when disowning as non-maintainer;
  previously, this was only done for display and not functionally.
  This check applies to Trusted Users' disowning of a package.

This style of notification flow does reduce our visibility, but
accounting can still be done via the close request; it includes
the action, pkgbase name and the user who accepted it.

Closes #204

Signed-off-by: Kevin Morris <kevr@0cost.org>

templates/requests/close.html

@@ -23,24 +23,6 @@
 
         <form action="/requests/{{ pkgreq.ID }}/close" method="post">
             <fieldset>
-                <p>
-                    <label for="id_reason">{{ "Reason" | tr }}:</label>
-                    <select id="id_reason" name="reason">
-                        {# Value 2 == "Accepted" status.
-                        See aurweb.models.package_request. #}
-                        {% if request.user.is_elevated() %}
-                            <option value="2">
-                                {{ "Accepted" | tr }}
-                            </option>
-                        {% endif %}
-                        {# Value 3 == "Rejected" status.
-                        See aurweb.models.package_request. #}
-                        <option value="3">
-                            {{ "Rejected" | tr }}
-                        </option>
-                    </select>
-                </p>
-
                 <p>
                     <label for="id_comments">{{ "Comments" | tr }}:</label>
                     <textarea id="id_comments" name="comments"