Cargo clippy updates

[citizen-stig]

Following things have been updated:

• 10 warnings: this argument is passed by reference, but would be more efficient if passed by value: https://rust-lang.github.io/rust-clippy/master/index.html#trivially_copy_pass_by_ref
• 4 warnings: identical conversion: https://rust-lang.github.io/rust-clippy/master/index.html#identity_conversion
• 2 warnings: writing &Vec<_> instead of &[_] involves one more reference and cannot be used with non-Vec-based slices: https://rust-lang.github.io/rust-clippy/master/index.html#ptr_arg
• 1 warning: unnecessary parentheses around method argument
• 1 warning: this .fold can be written more succinctly using another method: https://rust-lang.github.io/rust-clippy/master/index.html#unnecessary_fold
• 1 warning: this .into_iter() call is equivalent to .iter() and will not move the slice: https://rust-lang.github.io/rust-clippy/master/index.html#into_iter_on_ref
• 1 warning: redundant field names in struct initialization
• 1 warning: Consider removing unnecessary double parentheses