[wsinccxo] Factorization diagrams

Enhance Brent Yorgey's factorization diagrams so that a large prime p is handled as a single object in the center surrounded by the factorization diagram of p-1.

Need some care for a number like 23, which reduces twice consecutively 1 + 22 = 1 + ( 11 * 2 ) = 1 + ( ( 1 + ( 5 * 2 ) ) * 2 ), to avoid the two 1+'s from overlapping (or nearly overlapping) at the center point.  I think it forces the *2's to be handled first.

Special case 7 to be a single object surrounded by six objects. Orientation decision is similar to 2.