Initial refactoring of `displayz`

[shymega]

• Bump Cargo.lock and dependencies.
• Use cfg_attr to expose platform-specific APIs in the platform module, then export with pub use.
• Create initial common module for abstracting displays.
• Make examples only run on Windows - pending refactoring of Windows backend.
• Add lints.

Resolves #2.

[shymega]

OK, some updates. I've added a note to Resolutions, and wrapped get_edid in an Option.