458 - Keyframe widget indicator (arrow) enhancements - kf name on toolip

- Test if the kf name is empty to affect "No name" of the kf name
458 - Keyframe widget indicator (arrow) enhancements - kf name on toolip2

- Code readability,  add ( ) around kf name test
458 - Keyframe widget indicator (arrow) enhancements - micro Performance

- do not perform any operation if the key frame list is empty
Fix 626 - Key frame name losted on key frame move

- affect Widget_Keyframe_List::selected_kf description in any
case inside Widget_Keyframe_List::set_selected_keyframe
456 - Time indicator tooltip on keyframe drag and drop operation - progress

- add moving_tooltip_ a Gtk::Window* Widget_Keyframe_List private member
- creation and setup moving_tooltip_ in Widget_Keyframe_List contructor
456 - Time indicator tooltip on keyframe drag and drop operation - progress2

- add user_display_ a Glib::RefPtr<Gdk::Display> Widget_Keyframe_List private member
- get the pointer coordinate from user_display_
- show and move the moving_tooltip_ gtk::window when draging keyframe
- hide the moving_tooltip_ gtk::window on mouse release event
456 - Time indicator tooltip on keyframe drag and drop operation - progress3

- add moving_tooltip_label_ a Gtk::Label* Widget_Keyframe_List private member
- setup moving_tooltip_label_
- add moving_tooltip_label_ to moving_tooltip_
- update moving_tooltip_ setup
456 - Time indicator tooltip on keyframe drag and drop operation - progress4

- displaying the dragging time
456 - Time indicator tooltip on keyframe drag and drop operation - progress5

- display the dragging time according the global fps setting
456 - Time indicator tooltip on keyframe drag and drop operation - progress6

- cursor position from GdkEvent x_root and y_root (remove Gdk::Display stuff)
456 - Time indicator tooltip on keyframe drag and drop operation - progress7

- Display 2 lines tooltip : new time & old time
456 - Time indicator tooltip on keyframe drag and drop operation - progress8

- fix old time display when playing with both kf widget on same kf
456 - Time indicator tooltip on keyframe drag and drop operation - progress9

- Rewrite some doxygen comments
- Rename Widget_Keyframe_List::on_keyframe_changed
in Widget_Keyframe_List::on_keyframe_selected
456 - Time indicator tooltip on keyframe drag and drop operation - progress10

- Better positioning the handmade tooltip : up to the widget,
with y coordinate fixed.
Keyframe improvements