Substrate compatibility

[ascjones]

As part of a proof-of-concept to utilize scale-info in substrate, this issue will track all the changes in this crate in order to make it work.

• Add informational field type name Add informational field type name #30
• Consolidate common prelude for std and no_std and usage Consolidate common prelude for std and no_std and usage #33
• Derive TypeInfo for fields with associated types without bounds Derive TypeInfo for fields with associated types without bounds #20
• Optional serde feature Optional serde feature #34
• Parameterize CompactForm String for optional SCALE impl Parameterize CompactForm String for optional SCALE impl #35
• Use PortableRegistry for encoding and serializing Use PortableRegistry for encoding and serializing #40
• Add a compact flag to Field Add a compact flag to Field #42
• Handle more SCALE attributes: skip, index Handle more SCALE attributes: skip, index #44

For reference, all the above mentioned PRs are integrated into the https://github.com/paritytech/scale-info/compare/aj-substrate branch, which is the working branch I am using from my substrate branch PoC https://github.com/paritytech/substrate/compare/aj-metadata-vnext

[ascjones]

Superseded by #89