Configuration Control: line color and style

[fpurcell]

The walk line used on trip plans right now is a dotted sky-blue line. Similarly, transit lines are a solid navy blue line, when color is not specified in the GTFS. Not to mention that the BIKETOWN bikeshare stuff uses their proprietary Orange branded color (e.g., if another bikeshare company, ala Lime enters the Portland market, we'd want to change / have multiple colors), etc...

For many reasons (e.g., branding, basemap styles/colors, etc...), many of the default colors and line styling should be available to be overridden via configuration.

As a trial of this styling config idea, we'd like to see the above mentioned itinerary walk line and color be available for default style override via config.yml.

[msrichardson]

The gray carshare line is also hard to see on the aerials