Bug 19726: Move admin templates JavaScript to the footer: Preferences

Bug 19726: Move admin templates JavaScript to the footer: Preferences

This patch modifies the staff client's system preferences templates so
that JavaScript is included in the footer instead of the
header.

To test, apply the patch and test the JavaScript-driven features of
both the standard and local use system preferences:

 - WYSIWYG editor
 - Confirmation messages
 - Table sorting
 - Multiple selects (CoceProviders for example)

Signed-off-by: Claire Gravely <claire.gravely@bsz-bw.de>
Signed-off-by: Josef Moravec <josef.moravec@gmail.com>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>