The overall alignment of the flowpane's content within its width and height.

For a horizontal flowpane, each row will be aligned within the flowpane's width using the alignment's hpos value, and the rows will be aligned within the flowpane's height using the alignment's vpos value.

For a vertical flowpane, each column will be aligned within the flowpane's height using the alignment's vpos value, and the columns will be aligned within the flowpane's width using the alignment's hpos value.

Returns:  the overall alignment of the flowpane's content within its width and height