Omit Custom Request Guards, take 2

[dteare]

Adds support for excluding types from the generated TS interface. Especially useful for skipping over params that are created automatically via Rocket request guards.

This PR also:

• Includes params of type &str in the generated interface and maps them to string
• Maps some primitive Rust number types to number
• Hides debug logging in release configurations
• Makes output file optional, printing directly to STDOUT when not provided
• Improved formatting of generated interface

[!NOTE] This PR resulted from reviewing @AvaterClasher's PR #5. Technically, I should have pushed to the original branch but inadvertently used the review branch directly and decided to keep it. Thankfully all of @AvaterClasher's commits are preserved here with the proper attribution.

Closes #3.

Supersedes #5.