Bug 35187: Make sure HTML notices use explicit line breaks

Bug 35187: Make sure HTML notices use explicit line breaks

When a notices is marked as HTML, we need to use block elements
(p, div, li, etc.) or explicit line breaks.
This adds the line breaks where required.

Affects:

* ISSUEQSLIP
* ISSUESLIP
* TRANSFERSLIP
* CHECKINSLIP
* HOLD_SLIP
* WELCOME

The biggest change is the WELCOME notices. With this patch
it appears no longer on only one line, but properly formatted.

To test:

WELCOME
* Without patch
* Make sure your Koha can send email (set up SMTP server, KohaAdminLibraryAddress)
* Make sure your patron has an email set
* In patron account, use "More > Welcome email"
* Verify all text is on one line
* Apply patch
* reset_all to install new sample notice templates
* Repeat test, verify welcome notice is now nice

ISSUESLIP, ISSUEQSLIP
* Checkout at least 2 items
* Print > Print slip
* Print > Print quick slip
* Verify both look nice!

CHECKINSLIP
* Return both items
* Print checkin slip (button in list of checkouts)
* Verfiy... you know, that it looks nice!

TRANSFERSLIP
* Checkin an item from another library
* "Print transfer slip"
* Verify again.

HOLD_SLIP
* Place a hold on a record
* Return an item that can fill the hold
* "Print slip and confirm"
* Verify.
* Note: if you compare to before, this also removes a <> appearing instead
  of the city.

Signed-off-by: David Nind <david@davidnind.com>
Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>
Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>