Fix #270: on iOS, List doesn't scroll correctly when it is inside a deli...

Set position:absolute, width:100% and height:100% on List's inner node => The List is no longer sized by its children
Set width:100% and height:100% as default on List => The List's parent height must be defined, see List.md
Just to add that the bad impact of the changes can be seen for instance with deliteful/tests/functional/list/listbox-mark-2.html. The list is simply not visible anymore (it has a height of 2px). Except for the sizing issue, the DOM content is correct - the functional test does pass despite the height being broken.