CIs, UVs, and simple_UVs are the same thing

[rasmus87]

The calculation of both CIs UVs and simple UVs seems over excessive.
They all calculate the exact same thing correctly - but it seems error prone to do it in three different ways.

All three implementations calculate the exact same thing, and I would suggest using only one function and letting the other functions just refer to that one function.

The implementation of CIs looks cleanest and I would suggest the others just pointed to that.

[CWWhitney]

I have merged the functions.
Now UVs and simple_UVs all refer to the CIs function.
I am not satisfied that this is the ideal solution here but will leave it with these references for now. My thinking here is that if a researcher wants to calculate UVs or simple_UVs they should be able to find the formula in the vignette and the function in the package.

[KamilaBio]

@CWWhitney, Thank you for the development of the package! Is it possible to change the colors? which function do you use to change the colors of the CIs-plot?