Support for custom detection scripts for ConfigMgr Apps

With pre and post script customization, it would be useful to also allow custom detection script additions that can be merged in or sourced from the main detection script during synchronization. This would allow for those custom changes outside the base application to be validated during appeval cycles. I envision the script itself could be open ended, with perhaps some UI guidance to only write validation code and not use the space to make changes as with any detect scripts. The return value to the main detection script could be a simple pass/fail boolean. If the main detection script AND the custom script both return true, the clients will evaluate the application as being compliant.