Upgrade Data implementation to allow upgrading Sponge's Schematic Format

[gabizou]

With our Schematic format needing an update to support EntityArchetypes and Minecraft's Data Version to pipe not through DataFixers (which Mojang has not implemented yet on their own schematic format, because it's assumed that structures are still only somewhat used for creating structures in code).

Here's my proposal for changes necessary for Schematics v2 (or 1.1?) which will also affect how implementation is handled:

• Alter Entity#toContainer(), TileEntity#toContainer(), and ItemStack#toContainer() to include the "current" Data Version that Minecraft is using

  • Pipe pre-existing data through DataFixers to upgrade from whatever current version
  • Bump the sponge exposed DataVersion to allow fail fast detection whether some other data needs to be updated, or only the DataFixers need to be processed

• Properly implement setRawData to treat incoming data as if being read from NBT

  • Maintain the "unwrapped" Sponge formatted data, like position, types, etc. when absorbing the data, so that we don't have to change all our constants to use Mojang's constants
  • Document the format of our data and possibly their queries

• Improve DataView API We need to better the process and usability of DataView and throw exceptions when a passed in object cannot be serialized to primitive supported types

• Implement the proper support for using Keys and DataManipulators based on NBT.

  • Overhaul how NBT Processors are currently written, but actually make them usable.

• Provide a data upgrader for old schematics to new schematics. Treat old content versions as Sponge content versions due to current implementation of schematics.

This also lends itself to needing the Data layout documented for Sponge's implementation on the docs, likely as an advanced section, pinging @Inscrutable for input on that. Likewise, we need to update our Schematic specification.

[Inscrutable]

SpongeDocs has a Data section with a few sub-pages, but nothing at all on schematics. There would be more data stuff, but the Issue has gone cold since Saladoc went away, and we have few people who feel confident enough to write about it.
The aforementioned pages would need updating and extending after this PR goes through, if someone cares to walk through the how to use the final implementation. (I won't complain if anyone wants to try finishing out the current Data docs either).

[ImMorpheus]

@gabizou What's the status of this after the recent PRs ?

[gabizou]

Largely still relevant. Haven't bothered redoing any of the formats or updating the format spec for Sponge's internal formats on it's things like snapshtos etc.

[Inscrutable]

If we do write about Schematics in the docs it will finally deal with this old issue: SpongePowered/SpongeDocs#507