Provide methods to access value, unit etc. in Python code

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In Python code, it might be useful to do something like this:

import resultwizard as wiz

my = wiz.res("Important", 3.14, 0.02, "\J")

# then somewhat later in the code
print(my.value)
print(my.uncertainty)

Similar to what we already provide to LaTeX (e.g. \resultImportant[value]), we could also provide an API for the python code.