Bugfix XRPToDrops Conversion fixes #89

[JakeLardinois]

Additional info:

• NumberStyles.Float is a predefined combination of flags that already covers all the scenarios ie NumberStyles.Float ==
  NumberStyles.AllowLeadingWhite |
  NumberStyles.AllowTrailingWhite |
  NumberStyles.AllowLeadingSign |
  NumberStyles.AllowDecimalPoint |
  NumberStyles.AllowExponent. Bitwise & between flags like AllowLeadingSign & AllowDecimalPoint results in 0 — they’re different bit positions, so you’re OR-ing together mostly ineffective combinations. In short: most of the manually combined styles collapse to AllowLeadingSign | AllowDecimalPoint | AllowExponent, which is exactly what Float already provides — but with more completeness (whitespace handling).

• Removed duplicate "decimal.Parse(xrpToConvert..."

• Removed if (!(xrpToConvert is string)...) because its always false

• Used xrpValue directly in math

• Added CultureInfo.InvariantCulture to final ToString() to prevent unexpected formatting