Add elevation member to geo.latlng
Add support for z value
Add validate of z value in geojsonReader test case
Fix jshint issues
Assume sea-level if no value is given

In the future, we may have to define invalid value
Merge pull request #217 from OpenGeoscience/elevation-data

Elevation data
Merge remote-tracking branch 'origin/selection-api' into selection-api-updated