Blender Git Loki

Fix T39819: Decouple autosnap behaviour from time display

This commit cleans up and fixes some problems related to how the auto-snapping
behaviour in the animation editors works, resolving the issues mentioned in T39819.

1) "Nearest Frame" no longer snaps to the nearest second when time is displayed in seconds.
Instead, there is now also a "Nearest Second" option, so that either can be used
as needed instead of only when a certain time display is used.
2) A similar change has been made for "Time Step" - This is now "Frame Step" and "Second Step"
respectively.

Notes:
* Removed the unneeded getAnimEdit_DrawTime()
* Time Step/Frame Step don't work for Graph Editor yet (and seem to not have worked at all)
* NLA Editor also seems to be showing some weirdness now. Will be checked on.
* Cancelling nearest-second snapping doesn't work nicely, due to another bug with GraphEdit transforms.