Sell Half On Double

Notes:
- In settings leave 0 for actual price, or set a new price and the SHOD levels will change too.

版本注释:

Re-structured the code and provided more input options to user.

版本注释:

Added fees calculation to have them covered in selling price.

版本注释:

Updated the chart and marked fees section in code

版本注释:

I've updated the fee formula to be more accurate.