Status: only create User and Group when requested

[simeonschaub]

Potential fix for #182

[rofinn]

Hmm, the problem with just pushing this to getproperty is that you're potentially adding unnecessary work on duplicate accesses (e.g., print, string). I think a better approach might be to:

1. Correct the system path behavior to just call Mode(stat(string(fp)).mode)
2. Add additional error handling to libc and maybe a feature flag to support lazy evaluation of StatStruct field conversions?

[simeonschaub]

I'm not quite sure what you mean by

Add additional error handling to libc and maybe a feature flag to support lazy evaluation of StatStruct field conversions?

But the first suggestion definitely seems reasonable, will make another PR shortly