Port API changes from the Kotlin toolkit

[mickael-menu]

Changed

Shared

• A new Format type was introduced to augment MediaType with more precise information about the format specifications of an Asset.
• Fetcher was replaced with a simpler Container type.
• PublicationAsset was replaced by Asset, which contains a Format and access to the underlying Container or Resource.
• The ResourceError hierarchy was revamped and simplified (see ReadError). Now it is your responsibility to provide a localized user message for each error case.

Streamer

• The Streamer object was deprecated in favor of smaller segregated APIs: AssetRetriever and PublicationOpener.

And much more...