Remove HSV<->RGB conversion functions

[run4flat]

Maggie is adding these to a PDL::Graphics::ColorSpace module, so I do not need them anymore. The only thing I do need to provide is RGB->PrimaColor, along with the associated transforms.

[mohawk2]

It may be relevant that there's also a https://metacpan.org/pod/PDL::Transform::Color - but if Maggie's module needs updating, let me know as I have permissions on it.

[mohawk2]

Update on this: I have very recently updated P:T:C to use P:G:CS, and updated that to be so usable. I recommend P:G:CS for all this sort of stuff.

[mohawk2]

Further notes: having now read through the code, this module's needs are different from those solved by P:G:CS; that uses double for each colour-component (RGB, HSV, etc), while this module uses float+ for HSV, and a 32-bit int for RGB (one byte per R, G, B). Therefore, I think this issue does not need solving!

However, I do think it would be valuable to add literally any tests at all for the conversion utilities, and cribbing those from P:G:CS would make it super-easy, barely an inconvenience.