FYI: Accouncing retirement of BMPx

[Alexander Kahl]

I just had a private correspondence with Milosz Derezynski, the main dev
of BMPx where he confirmed the project was abandoned for the sake of a
new project, Youki, that will partly take over BMPx' code base
(feature-wise). As I cannot expect any support from upstream anymore and
I am neither willing nor capable (due to lack of time) to maintain the
project myself, I'm going start the retirement process now, close all
open and new tickets for BMPx and advise against (re-)adopting the
package.

- Alex