For 2.0: Fix links in Notebook Help Menu

[ellisonbg]

We need to update some of the links in the Help Menu before 2.0. This does that, but the links won't work until after #5337 is merged.

[minrk]

You have lots of 'merge upstream' commits here, want to rebase?

[ellisonbg]

Hmm, why am I getting these in my local master branch. I haven't changed my git workflow but recently started to see these. To get the latest from ipython master I do:

git co master
git remote update
git pull upstream master

That used to not give these merge upstream commits, but now it does. What am I missing?

[minrk]

If you made commits in your master, then pulled from remote master, you would get merges in your own master branch.

[ellisonbg]

Hmm, I don't think I ever make commits in my master...unless I did so by mistake. I will check that now...

[ellisonbg]

OK, cleaned up commits.