add .ToMetric() rounding

[tarakan12]

would be great to be able to round ToMetric() result so instead of 2.663982M it would spit out 2.66M.
it will take an optional parameter of rounding digits and potentially rounding direction

[JonCubed]

@onovotny any indication when this can be merged?

[aloisdg]

It looks nice, but I cant try it. (Can I debug it on Linux?)

[JonCubed]

@aloisdg @onovotny I see the pr has been approved, any updates when it can be merged?

[clairernovotny]

@JonCubed I'm aiming to get 2.2 out in early May, thanks!

[JonCubed]

@onovotny awesome thanks looking forward to 2.2