Add algorithm variants to docstring

[haesleinhuepf]

Is your feature request related to a problem? Please describe.
I was just using aydin.restoration.denoise.classic.classic_denoise and received an error because I didn't specify the variant parameter. When trying to find out what variants exist, I had to go to the source code.

Describe the solution you'd like
Would it be possible to add the available variants to the docstring?

Also this docstring appears misleading.

[AhmetCanSolak]

hello @haesleinhuepf ,

You are on point with everything you said. This is something I unintentionally broke and realized after the last version. I have some WIP to address all #203 . I will keep you posted.

[AhmetCanSolak]

hello @haesleinhuepf , just wanted to let you know #203 is merged. Please give it a try with our latest master branch commit and let me know what you think.

I feel I should also add a page/section to our documentation to describe the variants in depth later. Let me also know if you have opinions/comments regarding this.