LP1718782: Add the Srce fixed field to the Angular MARC editor

LP1718782: Add the Srce fixed field to the Angular MARC editor

To test:

1) Without using private browsing, open up a bibliographic record in
the Angular catalog MARC editor.
2) Notice that there is a gap between the ELvl and Audn fixed fields.
3) Apply this patch.
4) Open up the same bibliographic record, this time using private
   browsing (since the Angular MARC editor caches fixed field values).
5) Notice that the Srce fixed field is available between the ELvl and
   Audn fixed fields.
6) Notice that you can right click inside the fixed field to get a list
   of three possible values.
7) Repeat the test with different record types (e.g. BKS, SCO, VIS)

Signed-off-by: Jane Sandberg <sandbej@linnbenton.edu>