Bug 33478: Apply formatting to AR_SLIP

Bug 33478: Apply formatting to AR_SLIP

To test:

1. Enable ArticleRequests system preference in Koha Administration -> Global system preferences
2. Log into the OPAC
3. Do a catalogue search
4. Click the 'Request article' button for a record
5. Fill in some information and submit
6. Go to the staff interface
7. Go to Circulation -> Article Requests
8. Click the Actions menu next to your article request and choose Print slip
9. Confirm your format settings for AR_SLIP are applied

Signed-off-by: Lucas Gass <lucas@bywatersolutions.com>
Signed-off-by: Katrin Fischer <katrin.fischer@bsz-bw.de>