Replace VecMath with TeraMath

This PR replaces VecMath as far as possible with TeraMath. Some BulletPhysics-related content still uses VecMath through a wrapper.

This is mostly a simple replacement of methods. It does not refactor existing code, but allows us to do so later.

**TODO** (in a follow-up)
* Extract/adapt BulletPhysics `Transform` utility class in TeraMath
* Throw out duplicate Vector2i / Vector3i classes
* Refactor geometry classes in o.t.math (Rect / Vector3fUtil / etc. )
* Maybe remove VecMath from the collection of allowed libs for modules?

I wrote and reviewed this carefully. Please review it again to ensure that I did it right :smile: 
Note that TeraMath should be merged first (and uploaded to Jenkins with a proper version name (1.0.0?) and build.gradle needs updating).

Requires https://github.com/MovingBlocks/TeraMath/pull/23
It is copied and it is supposed to live only until the port is complete.