[BUG] size of ItemListCard

[enury]

The size of the ItemListCard was not fixed, when features are not grouped. This resulted in very long Cards that made navigating the map complicated.

We have corrected it by modifying the file SelectionPreview.scss, to add max-height and overflow-y:

 ul {
    background-color:#fff;
    max-height:300px;
    overflow-y:auto;
    list-style-type:none;
    margin:0;
    padding:0; 
    position:relative;
  }

(see commit).