Improve error messages

[chmp]

• Follow anyhow's display representations
• Unify error message format
  • lowercase / uppercase initial letter?
• Add relevant context for each error:
  • component (e.g., the relevant builder)
  • field path (Surface error more clearly for push_validity #202)
• Document the conventions
• Add context to deserializers
• Add context to tracers

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)
• Struct with String Field #97