* Added `Attachment#copy()` to all attachment type implementations. This lets you deep copy an attachment to modify it independently from the original, i.e. when programmatically changing texture coordinates or mesh vertices.
* Added `MeshAttachment#newLinkedMesh()`, creates a linked mesh linkted to either the original mesh, or the parent of the original mesh.
* Added IK softness.
+ * Exposed `x` and `y` on `SkeletonData` through getters and setters.