T3-939 Ability to get and set mimetype
Added getManifestPath()
writeAsJsonLD() support overwrite
added dct:conformsTo

This is to capture the "version" attribute in scufl2
Keep (load/generate if needed) Manifest. Saved on close()

TODO: Updating manifest for every operation!
Read remaining properties from manifest, such as authoredBy
Modified import
aggregates kept in a map. Supports repopulate
On repopulate, remove no-longer-existing aggregations
repopulate manifest on close
getAggregation() creates PathMetadata on demand
setAggregates from the given argument
open on desktop after closing
Should no longer make its own manifest
read OA annotations from manifest
Avoid null lists (just don't serialize empty lists)
Parse OA annotations correctly w/tests
Re-enable memory-efficiency-test