heatmap: Option to transpose the plot

[etal]

The current "horizontal" layout shows samples in rows, chromosomes in columns. A transposed or "vertical" layout would show samples in columns, chromosomes in rows. (Sometimes this makes a better figure.)

Consider the flags "-t/--transpose" or "-v/--vertical".

[tetedange13]

Hi @etal ,

I do not know if this is still a desired new feature, but I came up with something quite satifying: https://github.com/tetedange13/cnvkit/tree/35-vertical-heatmap

1. I first tried keeping up with BrokenBarHCollection, but verticalized plot was quite heavy to plot (loading all the time, zooming locked...)
2. Then I implemented a 2nd version using pcolor + a native Matplotlib colormap

=> Not perfect but seems consistent with "default / not vertical view", still some polish left
=> Also I could not reimplement --desaturate mode as I had trouble understanding the maths...
=> IMHO it should be possible to implement it directly inside the colormap using custom normalization (with a proper sigmoid function)

Hope this helps.
Have a nice day.
Felix.

[etal]

Thanks for sharing, @tetedange13 . Would you like to create a pull request out of your branch to make reviewing easier?