ToolSettings should allow should support of exit codes other than 0

[Sam13]

Currently a CakeException is thrown when a tool has other exit code than zero.

Since they are tools around (e.g. RoboCopy) which have different exit codes I suggest to add a list of valid exit codes to the ToolSettings class.

Or add a custom validation callback (Func<int, bool>) to validate the exit code on client side (similar to postAction) of Tool.Run()

[devlead]

Fixed by #1031