Dev fix: Loading from an initial draw position was broken

- I had inadvertantly broken the ability to set an initial draw position
  using `displayStart` or state saving with the small refactoring of
  _fnDraw and fnDisplayEnd. fnDisplayEnd must be called with
  settings._iDisplayStart set, which is now done simply by changing the
  order of calling a little.
Fix - thread #14114: State saved table breaks if columns reduced

- If the number of columns in the table were reduced, then the column
  filter state that was saved would be incorrect since it would define
  more columns that there were. Equally sorting could potentially be
  done on a column that no longer exists.

- There were a few work around in the code already to try and address
  this a bit, bit not satisfactorily as seen by thread 14114. The real
  issue was that the columns were being detected after the state was
  being loaded - ideally we want to load state after the columns had
  been detected and throw away the state saved if the columns did not
  match since the table might be entirly different.

- This is done by a little bit of reordering in the constructor, and
  actually simplifies the code a bit.
Dev: All the latest changes built into the main file