Separation of Scalar trait into another crate

[termoshtt]

Split Scalar trait to rust-math/cauchy

Objective

• Scalar trait itself is useful without LAPACK binding
• It is hard to deal with the dependency to ndarray-linalg due to LAPACK FFI

Summay

• ndarray-linalg::Scalar is split into two part: cauchy::Scalar and ndarray-linalg::Lapack traits
• Separated traits (e.g. AssociatedReal, Conjugate, ...) are unified into cauchy::Scalar
• RandNormal trait is replace to rand::distributions::Standard through rand feature of num-complex