Add AnimationController & strong typed fixed length array to UBJsonReader

UBJsonReader: See https://github.com/libgdx/fbx-conv/pull/18

This includes a first draft on an AnimationController. I've splitted it up into two parts:

BaseAnimationController:
Responsible for actually applying animations. It can either apply one animation (applyAnimation), blend two animations (applyAnimations) or blend multiple animations (begin(), apply(), end()). All these methods are protected for now, but perhaps it can be useful to have a derived class exposing these methods. This class introduces a Transform class for easily maintaining and blending transforms.

AnimationController:
A slightly higher level class that extends BaseAnimationController. It introduces a AnimationDesc class to keep track of animation states etc. which are pooled using a protected pool. Basically it has four methods:
- setAnimation: Set the current animation, without transition
- animate: Set the current animation, blending while transition with the previous animation if needed.
- queue: Queue an animation to be applied (using animate, thus blending) when the current animation finishes.
- action: Apply a (short) animation (using animate, thus blending) and then blend back to the previous animation.
Every animation has a loopCount (number of times to play) and speed (1f for normal speed). Besides that the update(delta) can be used to alter the overall speed. The speed or delta can be negative to play animations in reverse. For debugging purposes the members (current animation, queued animation, etc.) are public for now.

It also includes an Animation3DTest which includes a skydome and concrete texture.