arrow

ARROW-3088: [Rust] Use internal `Result<T>` type instead of `Result<T, ArrowError>`

Updates internal code to use existing arrow `Result` type.  Also, includes the following minor updates that do not deserve their own PR:
 - Removed `println!` statements that had been commented out but left in the code
 - Updated to use short-hand syntax where using identifiers that match the argument names when creating objects (i.e. `{field}` vs `{field: field}`)
 - Updated some `assert!` macros to more specific assert versions (`assert_eq!` and `assert_ne!`) to improve debug output

Author: Paddy Horan <paddyhoran@hotmail.com>

Closes #2448 from paddyhoran/ARROW-3088 and squashes the following commits:

0d923bb <Paddy Horan> Fixed lint issues.
21d8974 <Paddy Horan> Provide better debug info with more specific asserts
23f033a <Paddy Horan> Removed commented out `println!` calls
2caeb65 <Paddy Horan> Uses less verbose syntax for object creation
6d171f9 <Paddy Horan> Replaces standard `Result` with internal arrow `Result`