Add ST_ShortestPath to the list of functions
Add DO tests

This groovy script was really useful to me for writing the unit tests:

```groovy
import groovy.sql.Sql

def sql = new Sql(grv_ds)

5.times{ i ->
     5.times{ j ->
          println "oneToOne(DO, st, " + (i+1) + ", " + (j+1) + ","
          println "new PathEdge[]{"
          sql.eachRow("SELECT * FROM ST_ShortestPath('CORMEN_EDGES', 'directed - edge_orientation', " + (i + 1) + ", " + (j + 1) + ")") { row ->
               println "    new PathEdge(\"" + row.the_geom + "\", " + row.edge_id + ", " + row.path_id + ", " + row.path_edge_id + ", " + row.source + ", " + row.destination + ", " + row.weight + "),"
          }
          println "});"
     }
}
```