.center-block class isn't responsive

[andyrichardson]

There is a lack of ability to center element based on screen size.
This is inconsistent with the general class syntax of bootstrap 4, see below:

Text Center Evolution
<p class = "text-center"> Bootstrap 3 </p>
<p class = "text-*-center"> Bootstrap 4 </p>

Block Center Evolution
<img class = "center-block"/> //Bootstrap 3

<img class = "center-block"/> // Bootstrap 4 (current)

<img class = "center-*-block"/> // Bootstrap 4 (fix)

Conclusion
Create "center-*-block" classes

[saviomd]

I think .center-block should reset float too, so it could be used with columns and be less verbose.
ie.

<div class="col-xs-8 col-xs-offset-2 col-md-6 col-md-offset-3 col-lg-4 col-lg-offset-4"></div>

would become

<div class="col-xs-8 col-md-6 col-lg-4 center-xs-block"></div>

[RyanZim]

.center-block was removed in #19102 in favor of .m-x-auto. If it's going to stay that way, we should have a .display-block or .display-*-block class as recommended in #19343.

[cvrebert]

.display-*-block was rejected in #18410.
Closing this since, as noted, .center-block no longer exists.