Simplifies template chunks, validator
Adds Jasny fileuploader
Adds <a> tag disabler

Some of the page buttons are ``<a>`` instead of ``<button>`` for
various reasons.  Adding the ``.disabled`` class is purely visual in
this case, so the included javascript now returns ``false`` on the
click handler.
Fixes bug with non-primary file output path

Path joining was the wrong strategy, since the joined bits were not
path components.
Fixes logic for cancel page
Cancelled orders now included in completed list
Adds disabled state to detail page links
Adds clarifying note to main list
Adds readonly flag to context
Fixes wording of success message