Clone app objects to enable multiple embeddings

[akshayka]

Make it possible to clone an app object, so that the same app can be embedded multiple times (independently) in the same notebook.

I have another question (not sure if I can ask here or should open another request): I made a notebook (processor.py) that imports data from a file and processes them.
I need to process three files at the same time, to quickly compare the results, so I tried to import processor.py in another notebook (main.py) like that:

from processor import app

processor1 = app.embed()
processor2 = app.embed()
processor3 = app.embed()

but the output is the same, as the three processor were not different instances of app, but just three placeholders.
My workaround is to create three copies of processor.py and import them separately: is there any other way to obtain the same result?

Originally posted by @pcomepaolo in #3386