FlxStringUtil: Optimize and improve bitmapToCSV and prevent errors when farbling

[Geokureli]

Fixes #3541

• FlxStringUtil
  • Optimize arrayToCSV and therefore imageToCSV and bitmapToCSV
  • Detects browsers manipulating getPixel result for safety features and counteracts this in bitmapTo by getting the nearest mapped color
  • Add bitmap32ToCSVand image32ToCSV which does not ignore alpha
• FlxTilemap: Add overloads for loadMapFromGraphic deprecate the one that allows both invert and colorMap args
• FlxArrayaUtil: Add scale methods with overloads for arrays and 2d arrays
• FlxColor: Add getDistance and nearest methods for comparing differences in colors