Improve error messages

[chmp]

• Unify error message format
  • lowercase / uppercase initial letter?
• Indicate the relevant component for each error (e.g., the relevant builder)
• Include the field path in the error message (#202)
• Document the conventions

Known Issues:

• [ ] mismatched data types in particular for float coercion: F64 can accept U64, F32 cannot. Give a proper error message in this case and describe how coerce_numbers may help with Tracing
• [ ] Add point to corce_numbers for different number types (e.g., u64 accepting a f64)
• [x] https://github.com/chmp/serde_arrow/issues/97