[GRASS5] NVIZ bug fixes

Hello,

I have applied a couple of bug fixes to nviz and the ogsf library. The bug fixes address the problems reported in bugs #3646 and #3686 which deal with the movement between the new flythrough mode and the old "eye" / "center" mode.

I have also applied a fix to the problem where the elevation slider does not reflect the actual height at startup. Once the slider was activated the scene would jump to the correct position. I do not know if this bug was reported in the bugtracker.

With respect to bug #3686 the user can now set the "from" position without the scene swinging around. As an an added help, the user can click the stop button in the middle of an animation and the "eye" widget (if open) will set the position puck to the animation position. This should be helpful for fine tuning key frames. This has been added to both the animation and the key frame animation panels.

Please test and see if this fixes the reported bugs.

--
Bob