Fix first-order-reform coding style

Various style changes for `@treeVar` code. The only major changes were in `printTree.m`, where bugs were fixed to improve functionality.

@asgeirbirkis, especially take a look at the commits marked “Modifying behavior of ___ to accommodate complex numbers.” The codes were using `sprintf('...%2.2f...', number)` to print values of scalars; for complex numbers this prints `0.00`. I’ve replaced that with `num2str`, which does something better for complex numbers but gives unwieldy results in certain cases. For example, `num2str(100i, 2)` gives `0+1e+02i`. Do what you think is best.