Defold引擎中使用Spine骨骼动画的限制与指导

====== spine 的版本需求 ======
  * 只支援 spine 2.x 版本格式, spine 3.x 部分支援.(现在时间是 2020/01)
  * Defold supports most of Spine’s animation features, including inverse kinematics (IK).
  * Currently, Defold does not support animation keys that flip bones over the X or Y axis.
  * Defold supports mesh animation but only with bones, meaning that you can’t animate single vertices.
  * If you need to animate single vertices you can do that through a bone being 100% bound to that vertex only and animate the bone.
  * The Spine runtime implementation in Defold supports all Spine 2.x features.
  * The Spine runtime implementation in Defold provides only limited additional support for Spine 3.x features.
  * Make sure to use only Spine 2.x features to ensure compatibility with the Defold runtime!

====== spine 的规格需求 ======
  * 只需要输出 json 格式的 spine 动画档.
  * 不要输出 atlas 档案, defold 不支援 spine 输出的 atlas 档案; 必须进入 defold 建立自己的 atlas 档案, 然后将贴图档案汇入 defold.
  * 记得输入所有的贴图档案到 defold 的 atlas 专案里面(很重要).
  * 再次提醒: 不要输出 spine 的 atlas 档案, defold 不吃 spine 格式的 atlas 档案.
  * 支援 IK, 不支援 X轴 或 Y轴 翻转 bones 的 animation keys.
  * 只支援使用 bones 的 mesh animation; 不支援单一的 vertices animation.

====== 用DragonBones来重新输出Spine骨骼动画,并且可以自动将图档拆解开来 ======
<code C++>
[输出 Defold 可以正确使用的 Spine 骨骼动画]

1. 打开 Spine 骨骼动画档案 *.json
   检查动画档案的格式, 必须符合下面的格式类型.
   有可能会缺少 "skeleton" 的段落. 只要复制 "skeleton段落"的七行贴到 *.json 里面就好.
   
   << 以下为可以接受的格式 >>
{
"skeleton" : {
"hash" : " ",