Script mode implementation

[BrendanParmer]

NodeToPython v2.2 will come with a new Script mode, which is just the code for generating the node group without any add-on boilerplate. You can preview this with this branch #53

I've been deciding on a few different options on how to save this script.

1. Currently the script is saved to the Blender clipboard, so you can easily paste it wherever into a Blender text editor. However, it only works inside Blender. To get the script into an outside IDE, you'd need to recopy it from a Blender text editor.
2. Another option is just copying the script directly to the system clipboard, so you could directly paste it into an external script. This is an OS-dependent process, and I haven't found a way to do it with Python or Blender's default libraries. There are third-party libraries like pyperclip that take care of this, but I'm a little hesitant to make users have to download another external thing, especially since it seems you need admin privileges on Windows.
3. Another option is to just save it to a text file like before NodeToPython starting zipping addons together
4. Another option is just to paste it directly into a Blender textbox

If you guys have other ideas or suggestions, please comment down below!