Keyframe enhancements

- 548 - Display the keyframe's name (or "No name")
- micro Performance : do not perform any operation if the key frame list is empty
- Fix 626 - Key frame name losted after moving it from kf widget

**546 - Time indicator tooltip on kf drag**
- Tooltip is displayed up to the keyframe list widget, with y coordinate fixed
- 2 lines tooltip : time and old time