Sigfigs vs. uncertainty: integer interpretation is confusing

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Currently

wiz.res("Test variable", 630, 15)

yields: TestVariable = 630.000000000000. This is due to the 15 being interpreted as number of significant figures. This is confusing as one might expect to get back TestVariable = 630 ± 15 as is the case for

wiz.res("Test variable", 630, 15.0)

We should somehow circumvent the first behavior, e.g. only allow passing in sigfigs via a named keyword, e.g. sigfigs=15. Maybe this can be achieved with plum somehow. It would also be great to completely disallow the mentioned usage but I'm not sure one can prevent users from not passing in an argument as keyword argument.

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New wiz.res() proposal:

wiz.res("a", 3.14, 0.2, unit="\m")
wiz.res("a", 3.14, str(0.2))

Use Unit as keyword argument, then we don't have the problem with the strings type anymore that lead to difficulties with multiple dispatch.

Note that

wiz.res("a", 3.14, "\m")

will fail as "\m" will be interpreted as uncertainty. (For this case, we should have a really good error message.)
Therefore, in the docs, we should only use unit=. Advanced users might omit this in the case where an uncertainty is specified: wiz.res("a", 3.14, 0.2, "\m"), but we won't promote that use case in the docs.