Order is not preserved in collections

[goneall]

This is not really a bug, but I'm noting it here in the issues in case a recent change in behavior trips up any users of the library.

Prior to PR #144 the order of any lists or collections involving any SPDX elements was preserved (e.g. a list of external references, list of checksums). With the introduction of hash maps to improve performance, the order is no longer preserved.

Note that the spec does not guarantee any order and the RDF serializations have never preserved the order - this change will only be noticed in the Tag/Value, Spreadsheet, YAML, JSON, and XML serialization formats.

[goneall]

With PR #176 thanks to @carmenerre order is now preserved for most serialization formats except for RDF.

Note that RDF uses Jena for the underlying storage and retrieval of properties and order is not guarantied by Jena as mentioned above.

Since order has been restored ;) to the YAML, JSON, and XML formats, I'll close this issue as resolved.