Fix for #2969. Added ability to arbitrarily launch activities.

Change should be straight forward.  Only important change is the new start_activity path and startActivity function.  Had to add _startApp to support existing calls that are tightly coupled to the old startApp signature.
i see what you're doing here (having `args` default to the AUT data), just wondering if it would be a bit less verbose to simply pass in `this.args` as a parameter in the method above, so a check isn't needed here at all.