TopographyLayerRenderer Added

Created TopographyLayerRenderer.
Added the canvas object, and wired up the renderer to obtain the radar
site id and visible toggle.
Fixed a bug in OverlaysUrlBuilder.
CountiesLayerRenderer Added

Added the Counties Layer Renderer and wired it up in default.js to
obtain visible state and radar site id.
Fixed a bug in OverlaysUrlBuilder.js which caused the url to be rendered
incorrectly.