Add `vector` macro for initialization of `Vector` with argument-defined type and length

[chrissimpkins]

The approach will be similar to that used by the standard lib vec! macro for Vec types and will support the following initialization syntax:

Comma-delimited list of numbers with the same type

use vectora::vector;

use num::Complex;

let v_int = vector![1, 2, 3];
let v_float = vector![1.0, 2.0, 3.0];
let v_complex = vector![Complex::new(1, 2), Complex::new(-1, -2), Complex::new(-1, 2)];

[NUM; LEN] expansion syntax

use vectora::vector;

use num::Complex;

let v_int: Vector<i32, 3> = vector![1; 3];
let v_float: Vector<f64, 3> = vector![1.0; 3];
let v_complex: Vector<Complex<i32>, 3> = vector![Complex::new(1, 2); 3];