(Editor's Note: This story has been updated to reflect additional information disclosed by both companies.) Science Applications International Corp. said today it has agreed to acquire Engility in an all-stock deal worth $2.5 billion to create a $6.5 billion government services contractor. The move follows significant transformations for both companies. SAIC is a long-time contractor, but its current version was created five years ago when it was split in half; the other part of the company is now known...