Markup for: layout module

Meta issue: #1980004: [meta] Creating Dream Markup
Issue based on: #1898424: layout.module - Convert PHPTemplate templates to Twig

Questions:

Can we remove wrappers?
Can we do something with .layout-col* class? It's not so pritty.
And layout-* class may be ok with the module name, but it's a bit noisy in the final markup.

Markup proposal:

<div class="layout-display layout-two-col clearfix {{ attributes.class }}"{{ attributes }}>
  <div class="layout-region layout-col-first">
    {{ content.first }}
  </div>
  <div class="layout-region layout-col-second">
    {{ content.second }}
  </div>
</div>

<div class="layout-display layout-one-col clearfix">
  <div class="layout-region layout-col">
    {{ content.middle }}
  </div>
</div>

<div class="layout-display layout-two-col clearfix">
  <div class="layout-region layout-col-left">
    {{ content.left }}
  </div>
  <div class="layout-region layout-col-right">
    {{ content.right }
  </div>
</div>