[DS-1813] Unify configurations regarding SubmissionLookup step

From the 2 configurations that are used in the submission lookup service: 

a) dspace/config/modules/submission-lookup.cfg 
b) dspace/config/spring/api/bte.xml 

only the one is needed. The latter has been merged to the first one.

Moreover, this PR:

1) Renamed a method that @lap82 mentioned that has a misnamed name
2) Demo logic in the services has been removed
3) Fields that appear in the Details of a publication have been revised due to the https://jira.duraspace.org/browse/DS-1777
4) Fields that are empty does not appear in the Details form of a publication
4) A new config regarding the maxResults that should be fetched by the free test search of crossRef service has been added