Modify Primerize_2D.design() behavior

• Enable Primerize_2D.design() taking Design_1D() as input, and set this behavior as default;
• Add flag for forcing Primerize_2D.design() to run Primerize_1D.design() when manually input sequence, etc;
• Add mutation region display as an option in Design_2D().echo();
• Exclude plates with only WT well in Design_2D.save() for 'image' and 'excel';
• Use 3-digit well-position for Plate_96Well(), e.g. 'A01' instead of 'A1'.