Specs and implementation for dimensions and the off by one error for right/bottom
Positioning elements one pixel next/to last element not on the same

* e.g. do not take the rightmost pixel of an element to start a
  new element, take that + 1 - same goes for for bottom and top
* off by one errors...
* new return value for position_element to tell if we have to add
  one to either x or y when updating the current position. Best
  way I found to do this - would be cooler to update it straight
  in the position_element code but we have to wait with the update
  until after contents_alignment is called in case of a slot or so
  as this affects the height.