Story #3036

Updated by Tom Clegg over 7 years ago

(Certainly incomplete) list of changes/consequences:
* First step: allow clients to call collections.create without providing a uuid.
* Move current uuid values to portable_data_hash
* Fix clients so they pass the (expected) portable_data_hash instead of uuid (or pass neither) and use the uuid provided by Arvados, rather than assuming the new collection's uuid will be a content address.
* Add usual mutable fields like "name", "description", and "properties" to the collections table.
* Remove "all collections are owned by root" logic.
* Remove "add a permission link for me after creating a collection" logic.
* Update Workbench to use collections' "name" attributes instead of name links.
* Migrate existing name links in the database to become new collections.