Remove duplicate magics docs

[djv]

Issue #641

[takluyver]

-1: If I do %hist?, I want to see usage details, not an instruction to look somewhere else.

I think the magic system will need to specifically know about aliases, so that %magic doesn't show the same information repeatedly.

[djv]

Good point. Then it needs some code to do that.

BTW I took example from %ed

[takluyver]

Yep. The good news is that the magic system has just been refactored, so it should be easier to add things like this. Although it probably won't make it in before 0.13.

Once we've got such a system, %ed can be added to it as well. The inconsistency is probably just down to different developers with different priorities.

[fperez]

Marking for 0.14 so we can triage a bit...

[fperez]

Actually #2036 has a clean implementation by @bfroehle that supersedes this one, so I'm closing it now. Thanks for the contribution, @djv, it's just that we have a more robust implementation that better solves the overall problem.