Fix exporting the image.

There was a problem with rendering a map caused probably by my
experiments with the drag and drop connections, I had a connection in my
map without any nodes. I have added logging to catch every such case and
improved exporting to not crash the entire app.
Added node creation on drag and actions.

Dragging a connection into empty space was aborted up until now. Today
it started creating a new node and connecting to it.

Secondly, it is possible now to create actions (arrows showing shift in
time). You can do that by dragging from a circle on the right of the
node.
Added exporting actions.