Activate should default to "Not Handled"

[Brian Douglass]

Currently if you set a result to be "set_intercept_activation" with a uri, it will fail to act on the result when clicked. The logs will complain about a nullptr (which I believe is a reference to this: http://bazaar.launchpad.net/~webapps/unity-js-scopes/trunk/view/head:/src/bindings/src/scope-base.cc#L148 ). To get around this I've added an activate method that will return an activation response with "scopes.defs.ActivationResponseStatus.NotHandled", then the uri is opened. According to my experience with Go scopes and the scope api docs (https://developer.ubuntu.com/api/scopes/cpp/sdk-15.04.1/unity.scopes.ScopeBase/) the NotHandeled response should already be the default.