enable spectrum coloring for all styles

[dkoes]

probably implement this by interpreting spectrum is a property map of the resi with a gradient from the smallest to largest resi in the selection

[dkoes]

Have you verified this is implemented?

[K7S3]

I saw the issue #88 mentioned above. I arrived at a conclusion from there. Sorry if I'm wrong. Quoting the line you wrote, "The 'spectrum' colorscheme will eventually be just shorthand for specifying a mapping colorscheme from the residue ids, as opposed to the special purpose code it is now (this is the fix to issue #79)."

[K7S3]

I think I will reopen it now and leave it up to you to decide whether to close it or not, I might have very well been wrong to close this issue in the first place.