eulertoquat

代码说明：

  众所周知，欧拉角和四元数是存在对应关系的。后者用于导航等时不存在死区现象，而且，精度高，计算简单。(known, the Euler angles and quaternion is a correlation between them. Navigation for the latter did not exist at the Dead phenomenon, and with high accuracy, is simple.)