Add anti-virus scanner exclusions list

[ferventcoder]

Chocolatey should allow ignoring certain packages for anti-virus scanner when a customer has determined that they know a particular package has a lot of false positives and they want to allow the package to not check, which allows the binaries to be only be checked by their internal antivirus scanner.

This is great for upgrade all scenarios as it would keep the process of installs and upgrades seamless.

Related to #797.