In some cases, a POST might be sent to the server and there be no draft. In
such a case, neither the draft nor the body of the page can be inspected for
images. Even worse, in some cases the previous images might be unlinked from
the article without being relinked. Therefore, the images will no longer be
linked to the page and will likely be purged from the system.

Fixes #198

Fixes #138

Use a PHP setup which uses the built-in PHP tokenizer to parse and traverse
PHP scripts to determine (possible) access to uninitialized variables

Process inline attachments in thread entry and support inline images in
piped emails

Support inline images across the system, with draft support

Migrate to a single attachment table
    That way we don't need a new table for everything we need to attach an
    inline image to (like a signature, for instance)

Add richtext support for internal notes

Implement images on site pages

* Image paste in Redactor
* Make non-local images optional
* Placeholder for non-local images
* Fix local image download hover
* Don't re-attach inline images

And fix various lint issues, include adding the yet-undefined-but-referenced
deleteAttachment() function for canned-responses and faq entries

Also add a cron job to perform the task on demand
Change the implementation for Ticket::deleteAttachments to call this method
after simply removing all entries from the %ticket_attachment table