Add network to transport layer (#1158)

Closes #1153 

This PR populates the existing `network_type` field in the route table with highway route network information, using the most important value in cases of concurrencies.  In order to expose this value, two files `network_type.sql` and `update_route_member.sql` were moved from the `transportation_name` layer to the `transportation` layer.

Below is a representative zoom level 6 with motorways only shown for `us-interstate` network types.  This sample was generated from this PR using a [custom branch](https://github.com/ZeLonewolf/openstreetmap-americana/tree/selective-highway-zoom) of openstreetmap-americana.  This provides a simplified rendering of the highway network which excludes many minor motorway roads and sections.
![image](https://user-images.githubusercontent.com/3254090/126420985-c380b54b-a991-4a7c-a4c1-40a5cf5ec6b0.png)

Below is zoom level 6 on the current [openstreetmap-americana](https://zelonewolf.github.io/openstreetmap-americana/#6/42.148/-73.712).  Notice the many additional stubs, motorway islands, and minor routes which are present.  Instead of rendering `highway=trunk` to make this network look nice, we can instead suppress non-interstate roads and withhold motorway+trunk rendering to a closer zoom:
![image](https://user-images.githubusercontent.com/3254090/126421148-71e780ec-991d-4e38-a82a-85015b349e97.png)

layers/transportation_name/transportation_name.sql

@@ -184,7 +184,6 @@ FROM (
                 NULL::boolean AS indoor
          FROM osm_highway_point p
          WHERE highway = 'motorway_junction' AND zoom_level >= 10
-
      ) AS zoom_levels
 WHERE geometry && bbox
 ORDER BY z_order ASC;