Added map identifier method to jsonldconverter
Added mapidentifier to 020 map field
Merge branch 'jsonldconversion'

Conflicts:
	whelk-core/src/main/groovy/whelks/Marc2JsonLDConverter.groovy
	whelk-core/src/test/groovy/libris/whelks/plugin/Marc2JsonLDConverterSpec.groovy