The previous code `Toolkit.getDefaultToolkit().createImage()` does not read the image file into memory but Clipboard.setContents() on Mac seems to need an image that is already in memory.
- Added a `CTRL + +` to zoom in
- Added a `CTRL + -` to zoom out
- Added a `CTRL + 0` to reset zoom
- Minor refactor in classes names (removed "2" appended to GUI's classes name)