Read contour data from .e2e files

[jh88]

Hi Mark,

I added the code to extract contour data from e2e files. They are saved in a dict of list. The orders in the lists match your volume lists.

{
    'contour0': [
        np.array(...),
        np.array(...),
        np.array(...),
        ...
    ],
    'contour1': [
        np.array(...),
        np.array(...),
        np.array(...),
        ...
    ],
    ...
}

[marksgraham]

Thanks for adding this feature, it's excellent! I learnt about dict.get(key) from you, too :)