Apply a rotation to <code>this</code> quaternion rotating the given radians about the x axis.
<p>
If <code>Q</code> is <code>this</code> quaternion and <code>R</code> the quaternion representing the
specified rotation, then the new quaternion will be <code>Q * R</code>. So when transforming a
vector <code>v</code> with the new quaternion by using <code>Q * R * v</code>, the
rotation added by this method will be applied first!
@param angle
the angle in radians to rotate about the x axis
@return this
Apply a rotation to <code>this</code> quaternion rotating the given radians about the x axis. <p> If <code>Q</code> is <code>this</code> quaternion and <code>R</code> the quaternion representing the specified rotation, then the new quaternion will be <code>Q * R</code>. So when transforming a vector <code>v</code> with the new quaternion by using <code>Q * R * v</code>, the rotation added by this method will be applied first!
@param angle the angle in radians to rotate about the x axis @return this