Way to undo last action

[Redrield]

Is your feature request related to a problem? Please describe.
I was playing around with PathUI, and when I was trying to grab the heading and ended up creating a new point on the spline and dragging it out.

Describe the solution you'd like
A way to undo the last action done (consider action anything that happens to the path between mouse down and mouse up) This might include

• Adding a point
• Changing the heading of a point

Describe alternatives you've considered
For the specific issue that I had, being able to properly delete points would have also solved it. However that feature is currently broken

[gftabor]

Ties into #16