CO2.0: Update search to also search for fields on SPH child records

[jamieu]

Update lib/search.js to search for field on child record of an SPH (for details we do have on the parent).

Longer term we will need add additional fields to the SPH record (in the index) like description, so that these can be search along with the parents fields [index change].

See also.. https://github.com/TheScienceMuseum/collectionsonline/issues/1596 https://github.com/TheScienceMuseum/collectionsonline/issues/1566