Changed Curr. Span % on Sales Lines to be editable and to calculate the Unit Price

The column "Curr. Span %" in the Sales Order and Sales Quote is now editable. Formerly the "Curr. Span %" was just calculated. Now it is possible to define a "Curr. Span %" manually and with that to calculate the unit price of the current line.

When the "Curr. Span %" is set manually the Unit Price is marked as special price - like as if you would have changed the unit price manually.