use copy.deepcopy to prevent duplication of information when using export() several times

[khillion]

Hi Eric,

I realized that information written in the XML was duplicated when the export() method from the Tool class was used several times. Here I propose to use the copy.deepcopy() method to prevent this behaviour.

Thank you, Kenzo

[hexylena]

I'd never tried calling export multiple times. Interesting. I feel like there might be a more technically pretty solution than copy.deepcopy on self, but the tests pass so this is fine.

[khillion]

Thank you, I also think there must be another way to do it.