Round axis labels by Magnitude or BarUnit

[taoyouh]

Summary

• Separator postioning logic is changed in function LiveCharts.AxisCore.PrepareChart() of project Core40:

  • The bottom separator are always positioned first;
  • The position of bottom-most separator is caculated by rounding instead of truncation;
  • The positions of not only the bottom-most but every separator will be rounded to m (which equals to Unit or BarUnit, or Magnitude if not set);

Solves

• Solves issue Axis label rounding issues #918 :

  • When using truncation, values like 1.9405 (which can't be accurately represented in binary floating-point numbers) will be truncated to 1.94049, but 1.9405 is the real value people wanted.

• Solves bugs if separators comes from negative number to positive number:

  • If the data ranges from -0.15 to 0.15, the separator in the middle is placed at about 1.388E-17 but not 0. This is because -0.15+0.05+0.05+0.05 equals 1.388E-17 in binary floating-point calculations. Rounding the values should solve the problem.