[vector-api] ol.format.IGC

This PR demonstrates how the `ol.format.Format` architecture is able to extract features from formats that only include geometries. It also gives a real world demonstration of rendering complex geometries. Zoom in to see more detail.

(The Travis build failed, I don't understand why. Ca fonctionne chez moi...)


@Turbo87... this might be relevant (P.S. more cool stuff to come with IGC files: they're four-dimensional and so they're a great test bed for ol3).