Added more unit tests against significant digits after radix
Added more unit tests against significant digits after radix

- Fixed (hopefully) an issue with tests failing when running on a machine with a different culture.
- Reorganized formatting threshold tests to use TestCase attribute because it removes duplicate code..

BoGrevyDynatest/UnitsNet,anjdreas/UnitsNet,maherkassim/UnitsNet,BrandonLWhite/UnitsNet,maherkassim/UnitsNet,BrandonLWhite/UnitsNet,Tirael/UnitsNet,neutmute/UnitsNet,anjdreas/UnitsNet