Inkscape animation - Support for layers and motion tween using paths

It still exports the frames as a PNG series, which can for example be made into an animated GIF using GIMP. The biggest updates are support for multiple layers, and motion tween along a path. There is also a new option that enables you to make all keyframes visible, which is very useful if you want to move, scale or rotate your entire animation. An "insert keyframe" option has been added as well, it works by traversing the keyframes backwards looking for the latest drawn keyframe, and copies its contents to the chosen one, eliminating the need to copy keyframes manually. To do: - enable renaming layers - enable re-ordering of layers (this can be done through the built-in Objects dialog, though it won&be mirrored in the animation layer dialog) - enable deleting layers - scale tweening - rotation tweening - path (node) tweening - raster cached playback