wordpress: New app to manage a WordPress site/blog

- Use php-fpm instead of using mod-php.

- Create database and setup permissions manually. Tables and initial data are
created during the initial setup process done by WordPress. Database upgrades
are handled by WordPress. Minor versions are upgraded automatically and major
version need user intervention.

- Backup/restore functionality including database.

- Install recommended extensions for performance.

- Setup and run cron jobs to ensure that scheduled publications are
completed (among other things). Service has systemd security features. Timer is
set to run every 10 minutes.

- Functional tests for adding/removing posts and backup/restore.

- Increase file upload size limit to 128MiB.

- A private mode (default) for keeping the setup process secure. Should be
disabled after first setup is completed. This uses a new approach using
file-based flag for different Apache configurations.

TODO:

- Find a nice way to allow WordPress to upload plugins/themes. Currently this
operation files and users are expected to manually scp the files to
/var/lib/wordpress/wp-content/{plugins,themes} directory.

Tests:

- Functional tests.

- Schedule publishing of a post. Notice that post got published.

- Test uploading a file larger than 2MiB.

- Test enabling permalinks. This leads to nicer looking URLs.

- Test adding images to posts/pages.

Signed-off-by: Sunil Mohan Adapa <sunil@medhas.org>