RouteBuilder: a way to create a custom route to follow!

[misaugstad]

Resolves #3079
Resolves #1702

Adds a new page called RouteBuilder that allows you to build your own route to follow (and share it with others)!

How it works:

1. You can create a route by clicking on the streets that you want included (the first one you click on is where your route begins)
2. You can select and deselect the streets at will
3. When you've finished building it, click 'Save route' to upload it and save it in the database
4. You can then copy a URL to the clipboard for sharing with others (/audit?routeId=42), or click on the 'Explore route' button to start exploring it!

Some limitations and room for improvement:

1. There is currently no way to see other users' routes unless they share the URL with you
2. You can't see previous routes you made, edit them, name them, or delete them! Though the back end is set up for these operations.
3. We aren't putting any thought behind which way to orient users when they start a route. If a route is contiguous and doesn't loop, then we should really pick which direction they point on their first street!

Other TODOs (will create tickets when it's not late and I have time!):

1. I want to add our mapbox token as an env variable so that people can't use ours and use up our free credits!
2. Need to do a lot more testing with routes ending on a jump or on streets with no imagery, etc.
3. The front-end code related to neighborhoods looks SO bad right now, because "routes" are just kinda thrown on top of them. Much to clean up there.

Screenshots

Things to check before submitting the PR

• I've written a descriptive PR title.
• I've added/updated comments for large or confusing blocks of code.
• I've included before/after screenshots above.
• I've asked for and included translations for any user facing text that was added or modified.
• I've updated any logging. Clicks, keyboard presses, and other user interactions should be logged. If you're not sure how (or if you need to update the logging), ask Mikey. Then make sure the documentation on this wiki page is up to date for the logs you added/updated.

[misaugstad]

I also need to look back through this code and add more comments and clean some stuff up, but I wanted to get this out tonight!

[jonfroehlich]

Wooohoo! Great job Mikey!!!