Fix route costs in graph_route_example

For some reason, the graph_route examples have evolved into a broken state.

Basically, road length is taken without considering the earth radius.
Which leads to the following output:

distances, all in KM
Boston          - Chicago         -> through the air: 1370 , over the road: 0   
Boston          - Houston         -> through the air: 2568 , over the road: 0   
Boston          - Los Angeles     -> through the air: 4192 , over the road: 0   
Boston          - Miami           -> through the air: 2025 , over the road: 0   
Boston          - New York        -> through the air: 303  , over the road: 0   
Boston          - Phoenix         -> through the air: 3694 , over the road: 0   
Boston          - Washington DC   -> through the air: 641  , over the road: 0   
Chicago         - Boston          -> through the air: 1370 , over the road: 0   
Chicago         - Houston         -> through the air: 1496 , over the road: 0   
Chicago         - Los Angeles     -> through the air: 2822 , over the road: 0   
Chicago         - Miami           -> through the air: 1912 , over the road: 0   
Chicago         - New York        -> through the air: 1147 , over the road: 0   
Chicago         - Phoenix         -> through the air: 2333 , over the road: 0   
Chicago         - Washington DC   -> through the air: 960  , over the road: 0   

cost is mostly between 0 and 1, and later gets divided by 1000.

The bug is rather obvious: You need to use the haversine strategy
for linestring length as well, so that the distance though air
and over the road have same units.

With this commit applied, the output looks like this now:

distances, all in KM
Boston          - Chicago         -> through the air: 1370 , over the road: 1572
Boston          - Houston         -> through the air: 2568 , over the road: 2931
Boston          - Los Angeles     -> through the air: 4192 , over the road: 4811
Boston          - Miami           -> through the air: 2025 , over the road: 2875
Boston          - New York        -> through the air: 303  , over the road: 330 
Boston          - Phoenix         -> through the air: 3694 , over the road: 4327
Boston          - Washington DC   -> through the air: 641  , over the road: 704 
Chicago         - Boston          -> through the air: 1370 , over the road: 1572
Chicago         - Houston         -> through the air: 1496 , over the road: 2049
Chicago         - Los Angeles     -> through the air: 2822 , over the road: 3263
Chicago         - Miami           -> through the air: 1912 , over the road: 2253
Chicago         - New York        -> through the air: 1147 , over the road: 1252
Chicago         - Phoenix         -> through the air: 2333 , over the road: 2971
Chicago         - Washington DC   -> through the air: 960  , over the road: 1101