contacts: Remove ContactEntry and add Unsubscription

This change removes the unused `ContactEntry` model and the `subscribe` view and
replaces it with an `Unsubscription` model and an `unsubscribe` view. It works
similarly, but is intended to be used with the `list-unsubscribe` and
`list-unsubscribe-post` headers.

Remove summit_registration Django app

Has some typos suggesting that the code was never completed or used.

Defer JavaScript loading

This avoids waiting for the JS to download before rendering the page.

Move the content templates/files into `conservancy/content`

These were previously intermingled with the static content in `conservancy/static`.

blog: Retain author/tag when changing pages in entry_list

Denver noted that the author query string was being lost when you select a page
by page number. This change fixes it.

Move fundraiser calculations to model

This changes simplifies the template and adds correct pluralisation of
hours/hour remaining.

usethesource: Allow logged in users to edit/delete their own comments only

Unless of course they're given the "change comment" and "delete comment"
permissions, with which they can change or delete any comment.

Use decorator syntax to register admin handlers

Same-same, just marginally neater.

Move the content templates/files into `conservancy/content`

These were previously intermingled with the static content in `conservancy/static`.

Remove unnecessary `admin.autodiscover()`

Since Django 1.7 this is done automatically.

Delegate management of canonical URLs to Apache

This middleware is mostly redundant:

* redirecting to canonical URLs can be done more simply in Apache
* appending a forward slash is a default in CommonMiddleware now
* we're no longer using Squid cache

May need to update Apache to strip/redirect trailing "index.html".

Fix strange issue with ParameterValidator settings

When imported at top-level, `settings` was a Python module, rather than a Django
settings object. Not sure why.

Make bin/deploy abort if there's an error with `git push`

For example, your push failed because there's upstream changes.

Switch settings to use "the one true way" approach

The advantage of this approach is that the production and dev configurations are
in version control, so there's less opportunity for surprises.

As advocated by Jacob Kaplan-Moss (OSCON 2011) and Two Scoops of Django book.

Remove deprecated `ifequal` and `ifnotequal` tags

These have been replaced by `{% if x == y %}` type tags.

Switch from `url()` to `path()`

Path is the new way to handle simpler routing rules.

Switch from "restart apache2" to "reload apache2"

No need to do a full restart. Reload will be marginally faster.

Document the new deployment approach

Also mentioned linkchecker.

Rewrite the `index` view to avoid risk of path traversal

I've simplified this view by removing the custom HTTP error handlers, Python 3.5
exception handling and adding documentation.

Move Python code out of the "conservancy/static" directory

Having Python code in "conservancy/static" is a bit suprising to people familiar
with Django. The name "static" is usually reserved for assets like CSS, JS and
images.

I'm moving `conservancy/static/views.py` to `conservancy/views.py` and removing
`conservancy/static/__init__.py`.

fossy: Add created_time to CommunityTrackProposal model

Also move templates into app.

Fix mistaken rename

I meant to rename the deploy script, not the deploy directory.

Load JS through Django's staticfiles app

This avoids the need for adjustments during development and allows production to
be served under a single /static declaration in Apache.

Remove reference to old jQuery

This was 404ing anyway.

Add a basic script to "push" deploy

Currently updates are published by the "conservancy-www-update.sh" that does a
"pull" deploy with a 5-minutely job that runs on the web server. This doesn't
run `migrate`, `collectstatic` or restart the application, so certain types of
changes don't take effect, and even template changes often don't due to caching
template loader.

This script allows you to deploy more significant updates on-demand, but
requires SSH access.

podjango: Use `or_` instead of lambda

Easier to read.

Remove unused ccs-upload feature

Use the Source uploads now go to a NextCloud anonymous upload.

Move /cast/ to /cast/the-corresponding-source/

This makes room for addition of other podcasts later.