Create new prank UI should input for schedule

[goldbergyoni]

Why: right now, when someone creates new prank, the scheduling (when it will trigger) is hard-coded

How: First, read the schedule JSON and the schedulers we support (~/lib/schedulers). In the create new prank panel, let the user select scheduler type and the corresponding properties. For example, if the user selects the one-time-schedule then he should be able to set the properties fadeOutInMS and delay