- do not assume that input vector dir is normalized.

  The conversion formula used is valid only for unit quaternions.
  If a user passes a zero quaternion by mistake, the resulting matrix is
  identity. This is very confusing since multiplying by a Transform3f containing
  0 as a quaternion results in identity Transform3f.

  adding a test.

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fix the crash caused by the typo in intersect_Triangle

change the normal direction returned for triangle-triangle intersection, now it is from object 1 to object 2, consistent with shape intersection returned by libccd and gjk.