Bug 15594: preserve sequence of 260 subfields in (staff) detail page

Bug 15594: preserve sequence of 260 subfields in (staff) detail page

When ordered $a$b$a$b$c in the MARC object, 260 subfields are displayed
$a$a$b$b$c.  This goes against the standard.

This patch preserves the order.

0) create a notice with $a$b$a subfields.  In that (mixed) order.
1) Go to staff detail page and see the fields displayed as "aab"
2) apply the patch
3) validate the aba display.

Signed-off-by: David Nind <david@davidnind.com>
Signed-off-by: Nick Clemens <nick@bywatersolutions.com>
Signed-off-by: Fridolin Somers <fridolin.somers@biblibre.com>