Ol3-Cesium 1.3 release


I am pleased to announce version 1.3 of Ol3-Cesium, based on Ol 3.3.0
and Cesium 1.7.1.

This version contains a new method for computing a bbox in Cesium, bug fixes
and now use the Cesium lookAtTransform method.

Thank you to all contributors of Ol3, Cesium and Ol3-Cesium.