Fix quota bar width, and indicate almost full storage

When the quota is set by the admin to a value below the used space, the bar extends to make the personal page scroll horizontally. This fixes it.

Also adds a minimum width of 1% so it’s apparent how the quota bar will look. I know it’s incorrect, but otherwise it will look strange because it’s just empty.

Now the quota bar is also colored (in the notification yellow) when storage use is over 90%.

Please review @owncloud/designers 
Maybe make a CSS class of it. Otherwise theming is hard