interactive -- flag to run phc -p or phc -m in interactive mode

There are too many options for the path trackers in phc -p to wrap them properly within the trackPaths() method. With interactive turned on, the user can tune all parameters of the path trackers, in the same way as running phc -p.

The option interactive is also supported to run the polyhedral homotopies to solve random coefficient systems with phc -c, in the mixedVolume function with the option StartSystem set to true.