Create an Orthographic view mode

[jscastro76]

Related to #154
Mapbox-gl-js doesn’t have an orthographic camera option, indeed the FOV is hardcoded internally to Math.atan(3/4). Despite this FOV is not an init param of the map, is accessible through a private variable of map.transformation._fov, there’s a risk that Mapbox will convert this into a non-accessible member in the future.
Three.js has a pure OrthographicCamera object, but if we use it then the depth calculations for the matrixes and raycast will be wrong as they are developed for PerspectiveCamera

So, the best option seems to change first Mapbox camera FOV to mimic the Orthographic camera view in the best way possible and then replicate this view with Three.js PerspectiveCamera that will keep the right transformation matrixes and depth calculations

[jscastro76]

If map.transform._fov < 1.8 deck gl manages really bad the fill-extrusions

[jscastro76]

After many different tests and approaches, and considering Mapbox does not fully support an orthographic camera, we will add two different options:

• To have a full orthographic view through an init param orthographic: true, this will create a THREE.OrthographicCamera and related calculated Matrixes. It will adjust the map.transform.fov to the minimum possible (can't be 0 due to Mapbox limitations). IMPORTANT NOTE This view will present issues with fill-extrusion layers as this .
• To have any desired FOV perspective provided in degrees, from 0.2 to 1.0 values. It will keep the THREE.PerspectiveCamera and current view through another init param fov: _degrees_