Bug 16677 - Use abbr for authorities linked headings

Bug 16677 - Use abbr for authorities linked headings

In authorities search results, UNIMARC flavour, linked headings are displayed
with a link type : BT, NT, UF, RT.

This patch adds a abbr tag around those acronyms to know there meaning :
BT = Broader Term
NT = Narrower Term
UF = Used For
RT = Related Term

Acronyms are used because there can be a lot of linked headings, using abbr
will display the complete text on mouse over.

Test plan :

- Use UNIMARC database
- Create an authority with :
250 $a Heading250a
450 $a Heading450a
550 $5 a $a Heading550a
550 $5 g $a Heading550g
550 $5 h $a Heading550h
- Save an index zebraqueue
- Go to intranet authorities search
- Search for "Heading250a"
- You see :
Heading250a
Heading250a
UF: Heading450a
RT: Heading550a ; BT: Heading550g ; NT: Heading550h
- Move your mouse over the acronyms, you see a tip with the complete text
- Same with opac authorities search

Signed-off-by: Frédéric Demians <f.demians@tamil.fr>
  Works as described. Translatable.

Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>
Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>
(cherry picked from commit b9e47f135e036232b00cd3b24bb25ea0c6a9291e)
Signed-off-by: Frédéric Demians <f.demians@tamil.fr>