Add support for a new output format : GeoJSON

[fulups]

• add new GeoJSON output format

{ "type": "FeatureCollection", "features": [ { "type": "Feature", "geometry": { "type": "Point", "coordinates": [118.0,9.0,54] }, "properties": {"aaa": "test 1","bbb": 1,"ccc":"2012-01-01:00:00.000Z", ...}, }, { "type": "Feature", "geometry": { "type": "Point", "coordinates": [14.0,2.0,12] }, "properties": {"aaa": "test 2","bbb": 2,"ccc":"2012-01-01:00:00.000Z", ...}, } ] } 

• update README for this new format

• update test cases for this new format