Removed "format" from Document, replaced with more detailed contentType.
Introducing new brand of Whelk – HttpWhelk, capable of setting
contentRoot.
Added specific type of record to contentType
Implemented new type sorting in Elastic.
Suggest no longer a separate whelk, instead it's a general API
attachable to any whelk.
For generic _find API, moved type to query param instead of path. Adding
rootwhelk last to prevent shadowing other whelks.
Implemented simple way to track origin when doing oaipmh, dump or file
imports.