PCA works only for f64

[jorgehermo9]

PCA algorithm is only implemented for f64. Is there a reason for this? Can't it be implemented for trait Float?

I can take look at this over the next few days if no one else wants too

[bytesnake]

Depends on rust-ndarray/ndarray-linalg#275, this is already possible in the native Rust implementation but for fast LAPACK not yet

[YuhanLiin]

While the f32 impl would be broken when we use LAPACK, by default we use the pure-Rust linalg library instead, so f32 should work. I'll see if I can enable f32 for the pure-Rust library only without too much copypaste.