new date inserted on wrong header when shifting dates with elgantt-header-type set to 'outline

[legalnonsense]

Set the elgantt-header-type to 'outline. Shift a date. It will likely re-appear on the wrong header line because there is a problem with elgantt-get-header-create.

Two solutions:

1. Write a real elgantt-get-header-create that isn't a clusterfuck of half-assed code
2. Get rid of date shifting, and all of the many problems associated with it.