[Bf-codereview] Node socket selection reimplemented (issue 5727064)

[brechtvanlommel at gmail.com]

There does not seem to be any obvious way to deselect sockets, so when
making links I'm now always left with unwanted selected sockets.
Clicking a second time on the socket, or dragging to make a link should
deselect the socket I think.

Maybe this tool could be simpler, and not rely on a make links operator
at all: just click once on a socket to make it selected, and then click
on another socket to make a link it. That way the existing operator can
keep working, and it's faster to use too.

http://codereview.appspot.com/5727064/