GPX driver for H2 spatial

This PR introduces a GPX parser to import a GPX file in a H2 database.

The GPX parser is able to read the 1.0 an 1.1 format. It uses the java xml api and its bases on SAX event handler.

The syntaxe is expressed as 

```sql
CALL GPXRead('/tmp/mygpx.gpx', 'tableName');
```

When a GPX file is parsed many tables are created. It depends on the data contained in the file.
 
 - the input 'tableName' + the suffice _waypoint stores all the <wpt> elements,
 - the input 'tableName' + the suffice _route stores the <rte> elements. The <rte> element is also decomposed in a   'tableName' + the suffice _routepoint that stores all waypoints of a <rte>,
 - the input 'tableName' + the suffice _track stores the <trk> elements. The <trk> element is also decomposed in two tables : 
      ** a   'tableName' + the suffice _routesegment that stores all segment (list of waypoints) of a <trkseg>,
      ** a  'tableName' + the suffice _routepoint that stores all waypoints of <tk> element.

About the GPX format more information can be found here : http://www.topografix.com/gpx/1/1/