Range queries

Completed implementation of range queries on location table using Postgres built in int4range type. This requires Postgres 9.2 and performs best with 9.3. If range types aren't available then queries will revert bioseg if available or vanilla queries. New installations of Postgres may still need to install gist for the indexes to work.

To use, replace `create-bioseg-location-index` in `project.xml` with `create-location-range-index`.

This will create an index of `int4range(start, end)` on the location table and queries will be generated to use it. The `create-overlap-view` task will also detect whether built-in ranges are available and use them instead of bioseg for the overlappingfeatures view.