* Fix attachments lagging behind their parents (#14818)
* Fix animation blending (#14817)
* Bring back cool guy as another .x smoke test
* Add .x mesh loader unittest
* Do bounding box & matrix calculation at proper point in time
* Remove obsolete `SAnimatedMesh`
Previously, compiling on Ubuntu 20.04 would fail with the system-provided JsonCPP
version (1.7.4). Which would satisfy the documented requirement of "1.0.0+".