Allow manual adding of page-breaks for printing

[enketo-issue-mover]

From @MartijnR on July 21, 2015 22:4

appearance="print-page-break" forces a page break just before this question. I think it would be good practice to prefix with "print-" for any appearance that is print-specific.

Copied from original issue: kobotoolbox/enketo-express#262

[enketo-issue-mover]

From @MartijnR on July 21, 2015 22:22

this would be particularly useful feature for groups and repeats