Use split window with two panels to compare Import functionality

Description:

One way to improve testing of our importers would be to create a form panel in the tool we want to import. We then have that tool generate the code for the panel. We import the panel and change the class/file name and generate our own version. We then have a dialog with a splitter window that contains both panels -- that let's us see the two panels side by side to verify that they look the same.

Note that we would have to be really careful with wxFormBuilder projects to ensure that the project is always saved fully expanded. Otherwise, you end up with diffs based on the expand/collapse state in addition to any real changes you make.