Add .yardoc and API.md to .gitignore
EAD export: fix schemaLocation; add XLink namespace
EAD export: resource.ead_location should map to eadid[@url]
EAD export: place @langcode on language, not langmaterial
EAD export: Map linked agent role to @label
EAD export: wrap each note_definedlist item in <defitem>
EAD export: physfacet should be a child of physdesc
EAD import: map deflist[@numeration] to note_orderedlist.enumeration
Allow nil in ordered list enum; EAD export: nil attribute handling
EAD export: better handling for tags at start of note etc. content
EAD export: handle date['begin'].nil?
EAD import: map indexentry/ref[@target] to note_index_item.reference
EAD export: no <controlaccess> when no linked subjects or agents