Add travel times and anticipated arrival time

[flynnwastaken]

When are people arriving? When are they leaving? We have their trip start times and return times and departure points, but figuring out how long they'll actually be in the field doing canvassing is somewhat tricky based on what we have now.

This could include a trip planning feature by which you choose a destination and an arrival time (possibly derived from an event time and place set by the campaign organizer), and then it tells you when you leave from your departure point