Bug 35241: Fix markup errors in point of sale template

Bug 35241: Fix markup errors in point of sale template

This patch makes several markup corrections to the Point of Sale page,
fixing duplicate ids, invalid "selected" attributes*, a broken comment
tag, and an invalid "href" attribute.

* The "selected" attribute in this template is on a disabled <option>,
  so it can't be selected.

The patch also changes <div class="action"> to <fieldset class="action">
for consistency and better layout.

It makes some changes to the "Payment received" dialog in order to
improve visual consistency.

To test, apply the patch and make sure the EnablePointOfSale preference
is turned on.

- Go to Point of Sale.
- Test the process of adding items for purchase and collecting payment.
- After you submit the payment the confirmation dialog should look
  correct, and the "Print" and "Email" buttons should both work
  correctly.

Signed-off-by: Lucas Gass <lucas@bywatersolutions.com>
Signed-off-by: Katrin Fischer <katrin.fischer.83@web.de>
Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>