Fix: Column visiblity error

- When mouse down, we don't need to calculate from visible index to
  column index any more as we are using the column index already.
Fix: Ajax loading data with a predefined order (inc state) caused data
to be shown in the wrong columns

- Because the colun ordering was done before the Ajax data was loaded,
  the ajax arrays couldn't be shuffled. However, I don't think the
  arrays should be shuffled, particularly with DataTables' ability to
  use the original sorce data now. So just the column reference for
  where to get the data is used and the arrays are not reshuffled.
  Benefit of a bit faster as well.