Composes this font using a source font and a ModifyType for the operation.
The OGFont style is composed in a way that is similar to that used by Stingray.Grid.Style. ModifyType.ApplyNew copies styles from the source font to this font if they are set in the source, but not set in this font. ModifyType.Override copies properties from the source font to this font, even if they are already set in this font. ModifyType.Copy copies the font settings from the source font. ModifyType.Exclude resets attributes set in the source font.