Web: move error summary select all outside loop

Since this applies to all of the checkboxes, it should only appear
once.  (Attaching it to the two individual tables is confusing
because it implies that it operates on them separately.)
Web: move error summary JS to separate file

The layout template now checks for a scripts variable giving
a list of JavaScript scripts to be included.
Web: make jQuery available to scripts

Whenever the layout template is given a list of scripts to load,
it now also includes jQuery.  A copy of jQuery has been included
in the repository (the minimized version). jQuery has an MIT
license -- for more information see: https://jquery.org/license/
Web: attach select all JS via checkbox id

Use the checkbox's id attribute to attach the click handler
rather than using the onClick attribute.
Web: use change event for select all checkbox

This is a better event to use than the basic clicked event.
Web: use jQuery to set checkbox status

This avoids the need to iterate over the checkboxes manually.