Grid container / layout redux

This is a big layout system change, needed for the new graphic identity banding (full width bands of coloured background).

## Usage

```html
<!-- The container: does not do anything, but it impacts the children .facia-container__inner  -->
<div class="facia-container facia-container--layout-front">
    <div class="facia-container__inner">
        <!-- This is where the responsive layout happens -->
    </div>
</div>

<!-- For article-like facia containers, use .facia-container--layout-article -->
<div class="facia-container facia-container--layout-article">
    <div class="facia-container__inner">
        <!-- This is where the responsive layout happens -->
    </div>
</div>

<!--
    ***************************************************
    Banding comes for free, look:
    ***************************************************
-->

<div class="facia-container facia-container--layout-article">
    <!-- Yey, full width background! -->
    <div style="background: red;">
        <!-- put the border div here so that it goes full width -->
        <div class="container__border"></div>

        <div class="facia-container__inner">
            <!-- This is where the responsive layout happens -->
        </div>
    </div>
</div>
```

No gif, it won't allow me to upload one…