Bug 31371: Value builder for field 283

Bug 31371: Value builder for field 283

On page cataloging some plugins were added for subfields $2 and $a from field $283

Test plan:
    1)Go to Home > Cataloging > New record
    2)Section 2 - field 283 : it contains subfields $2, $6, $8 & $a
    3)Inputs are writable but notice that no plugins are suggested
    4)Apply patch and repeat 1) to 3)
    5)Values builders plugins are available for $2 and $a

Signed-off-by: Thibault Keromnès <thibault.keromnes@univ-paris8.fr>
Signed-off-by: Katrin Fischer <katrin.fischer.83@web.de>
Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>