Add an ignorable request validator parameter to ElectronNET workflow

[Daddoon]

Add an ignorable request validator parameter to ElectronNET workflow.

This is mainly for workarounding the new-window behavior that can do the URL validation event twice (the one from the onBeforeRequest, and the one occuring because of the LoadURL of the new window if the previous call was validated).

The only problem with this implemenation is that we may polute the original URI. Another workaround would be to disable cheking on URI we know that will be called twice, by registering them or disabling temporiraly the validator.