Update windows vadyarascan plugin

[eve-mem]

In PR #885 which adds the linux equivalent of vadyarascan there were changes made to allow more generic handling of the yara options.

This allows them to be pulled centrally from the generic yara plugin, so if updates or changes are made they filter through to the OS specific versions, or other future yara plugins.

The windows version was not updated at the same time, this issue is to track the need to update the windows vadyarascan so that it works in the same way. Currently the vadyarascan plugin itself manages the yara requirements.

This isn't a bug with the vadyarascan plugin, it works as expected, it is simply to change how the yara requirements are handled.

[eve-mem]

This can be closed as the update was merged in #1050.

After the merge it was noted by @ikelos that the processing f Yara options in general needs some work - this is being tracked in #1056