Exclude specified rule checks

[jangins101]

First off, thanks for such a great tool! As I've been using with PingCastle, I've had a need to exclude certain rules that may show up in the environment, but that I don't care to include in the scoring (e.g. they are acceptable risks within the environment). I didn't see a way to exclude specific rules, so I tried to take the simplest approach to providing a method for accomplish that from the command line.

Example: PingCastle.exe --exclude-rules S-PwdLastSet-45,S-PwdLastSet-90