Add shape_seq_index on gtfs_shapes

The index shape_seq_index (shape_id, shape_pt_sequence) drastically speeds
up accesses to individual shape points.
Update gtfs_tables_makespatial.sql

Fix for latest postgis. Some explanation here: http://gis.stackexchange.com/questions/57065/osm2pgsql-error-operator-class-gist-geometry-ops-does-not-exist-for-access-me
Merge branch 'addl-shape-idx'