Too many columns can not view all columns

[fzaninotto]

Porting issue #434 from react-admin, initially reported bymingchen

In list view, if I define a lot columns need to be shown, if the row length overflow the right of page, some columns can not be viewed and the page also can not support horizontal scroll.
For example, I define 12 columns, however only 10 can be viewed on page, 2 of them are in right of screen and can not be viewed.