Archive of the metadata (savefile) formats for lace. In charge of versioning and conversion.
The current version of the meta stays in latest.rs. If a metadata change
happens, everything in latest.rs goes to a version file, v<x>.rs. For
example if the first version of the metadata changes due to a change in the
State metadata, everything in latest.rs will go into v1.rs. latest.rs
will contain only metadata items that are different.
Implement MetadataVersion for everything. To make things easier, each file
should have a const METADATA_VERSION: u32.