Bug 21243: Regression: SRU mapping popup for bibliographic records is unstyled

Bug 21243: Regression: SRU mapping popup for bibliographic records is unstyled

This patch corrects a regression caused by Bug 21151: The include file
which adds CSS to the page was removed from the template.

To test, apply the patch and go to Administration -> Z39.50/SRU servers
-> New SRU server.

- Click the "Modify" button next to "SRU Search fields mapping"
- Verify that the pop-up window is correctly styled.

Signed-off-by: Claire Gravely <claire.gravely@bsz-bw.de>
Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>
Signed-off-by: Nick Clemens <nick@bywatersolutions.com>