Let user choose direction & order of streets in RouteBuilder

[misaugstad]

Brief description of problem/feature

This is something that would be helpful for controlled studies that we do. And there have been some requests from others who would want this! Still feels a bit advanced, so I'm not sure we want to have the UI for it shown by default.

An idea for how this might work

1. Clicking on a street adds it to the route and includes >>> symbols over the line, indicating default direction of the streets (right now it just adds the street, no direction info to show)
2. Clicking a second time reverses the direction (right now it just removes the street from the route)
3. Clicking a third time removes the street from the route
4. We could intelligently choose a default direction for subsequent streets based on the orientation of a previous street in the routes if they are connected