Files that are added/moved should take up the whole width of the pane, even if side by side view is selected

crucible's side by side diff sucks if its displaying an added/moved file - the right col is empty, and all the text is squished into the left col. we should detect added/moved files, and force a single col even if the preference is side by side (this only happens if text wrap is turned on. If text wrap is off, it correctly uses up the entire pane).