Show auxiliary data for the organization at the end

Show auxiliary data for the organization at the end

This is necessary in case the exporter wants to redirect output to a file.
Use built-in PHP functions to encode and output CSV content

Also add in the user email address after the user name.

This patch also adds an ::export() method to the FormField() class which
allows a field to define how the data should be formatted when exported.

Fixes #80

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

Addresses #589

This will facilitate a web-based export significantly easier

Adds a link to the scp/tickets.php page (Tickets) allowing for the export of
the data to CSV file. This is preliminary and still needs a few items:
  * An icon + button CSS definition
  * Support for alternate columns (staff assigned, etc.)

Also add beginnings of complex export support (PDF, JSON  and other
formats
to follow). CSV is fully supported for now.

And for brevity, add a Http::download method to allow for consistent and
browser-independent forced page content downloads