Fix spreadsheet view

• Fix the spreadsheet columns visibility consistency
  Columns visibility was restored only in the first opening of LidarView.
  For example :
  if you open the spreadsheet (using ctrl-t), hide a specific column, close the spreadsheet (using ctrl-t) and reopen it, the column wasn't hide.
  This was due to the check on the current object (if it was different thant the previous).
  Actually we want to update the column selection everytime the spreadsheet is displayed.
  Even if it's the same object or the same frame.

• Save the "Show only selected point" options of the spreadheet.
  The option is saved in the settings and reapply everytime the spreadsheet is opened
  When we open Veloview for the first time this option is set to false.
  This avoid having an empty spreadsheet an misleading the user.