Make the name of the command more consistent with the base project

[amtoine]

Describe your request

In the base project before bsp-layout, we have the Binary Search Partitioning Window Manager (the bspwm package) and the Binary Search Partitioning Controller (the bspc command).

I would like to ship the bspl command, i.e. the Binary Search Partitioning Layout manager command, to be more coherent with the bspwm base project 😋

and also to have a simpler command to type each time tests have to be done 😉

Briefly explain its use-case

Well, bspl would be the new command to use, i.e. it would be the one mentioned in the README and other places, but bsp-layout would still be installed with the whole lib for back-compatibility reasons.