Ergnomic improvements

[yoshuawuyts]

Feature Request

Detailed Description

The sleep-parser crate in its current state is a bit rudimentary. It correctly parses SLEEP headers, but the resulting artifacts aren't self-evident. We should express the different resulting structures as their own structs, and define the relationships between them.

Context

This should make the header types, and relationships between them more explicit.

Possible Implementation

• create a Bitfield struct
• create a Signatures struct
• create a Tree struct
• implement TryFrom<Header> for Bitfield
• implement TryFrom<Header> for Signatures
• implement TryFrom<Header> for Tree
• implement std::str::FromStr for Header
• implement std::str::FromStr for Bitfield
• implement std::str::FromStr for Signatures
• implement std::str::FromStr for Tree
• implement TryFrom<Vec<u8>> for Header
• implement TryFrom<Vec<u8>> for Bitfield
• implement TryFrom<Vec<u8>> for Signatures
• implement TryFrom<Vec<u8>> for Tree