Nand Lab: Improved

I have been improving Nand Lab on and off, and am now ready for another release. The main aspect of this one is a full under the hood rewrite, to make it easier to add new subprograms. But there are some user facing changes too, like making it less overwhelming to begin with, adding a top bar for better control, and support for multiples of the same program. Press the create button to add new instances of programs, and use the controls on top to move them around after selecting one. Next release will introduce saving and loading data, as well as an easier way to connect programs.