AnimationGadget : Improve Key tooltip
AnimationGadget : Improve Key tooltip

* time is now displayed in frames
* interpolation is displayed
* fields are shown on separate lines

ref #4418

GafferHQ/gaffer,hradec/gaffer,GafferHQ/gaffer,GafferHQ/gaffer,johnhaddon/gaffer,andrewkaufman/gaffer,hradec/gaffer,johnhaddon/gaffer,hradec/gaffer,johnhaddon/gaffer,andrewkaufman/gaffer,ImageEngine/gaffer,johnhaddon/gaffer,GafferHQ/gaffer,andrewkaufman/gaffer,ImageEngine/gaffer,hradec/gaffer,ImageEngine/gaffer,ImageEngine/gaffer,hradec/gaffer,GafferHQ/gaffer,andrewkaufman/gaffer,johnhaddon/gaffer,andrewkaufman/gaffer