Add Map Settings (Flexible Service Windows)

*Work in progress*

This commit creates a __map settings__ area, where users can set default service windows, speed, etc. These are inherited by bus lines as they are created.

- [X] Add basic framework for settings inheritance
- [x] Add speed, layover, cost per hour
- [x] Store map settings in ruby backend 
- [x] Add a "apply to all existing lines" button
- [x] Update time formula to work with post-midnight times (e.g. 8pm to 3am)
- [x] Design and style MapSettingsView
- [x] Figure out good default windows and window times (ask transit planners)
- [x] Figure out migration path for existing data