Bug 25864: Lower case fields for searching

Bug 25864: Lower case fields for searching

To recreate:
 1 - Have Koha using ES5 and Elasticsearch as search engine
 2 - Enable DumpTemplateVarsIntranet and DumpSearchQueryTemplate
 3 - Do a search in authorities using 'Search entire record' (abduction if using sample db)
 4 - Note no results
 5 - View the page source and find 'search_query'
 6 - Note the uppercased fields
 7 - curl 'es:9200/koha_kohadev_authorities/data/417?pretty'
 8 - Note all fields lower-cased
 9 - Apply patch
10 - Repeat search
11 - It works!

Signed-off-by: Heather Hernandez <heather_hernandez@nps.gov>
Signed-off-by: Alex Arnaud <alex.arnaud@biblibre.com>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>