Add support for user's canvas.
Add support for user's custom cursor design.
Insulate Dual Image and Canvas drawing modes.
Insulate defaults Dual Image and Cursor draw functions.
Fix error messages.
Rename template in format, and canvas in design for desambiguation.
Add a user-defined design as an example.
Add support for loading integrated default designs as "themes".
Homogenize return types for design management functions.
Rename loadPredefined design into fetchDesign.
Reindent and reformat comments.