cider's namespaces and vars should be filtered pretty much everywhere

[bbatsov]

In a lot of places (e.g. apropos, the ns browser, etc) the users can see cider's namespaces and vars. We should filter those out (although we also need a way to not filter them while hacking on cider itself).

[ckoparkar]

I'd like to give this a try. Two approaches I can think of:

• Put a filtering fn in cider somewhere, and a custom var which would contain the filtering prefixes.
  Then, all functions, cider-sync-request:*, would filter out the configured prefixes.
• Or, we could add another param to middleware requests, something like filter?, which would pass the prefixes and then the middleware would take care of this.

Thoughts ? I like the second one better.

@bbatsov @Malabarba

[expez]

We already do this in the middleware for the dependencies we've munged with mranderson.

[ckoparkar]

@expez Oh. Are you referring to the inlined-dependency fn? Guess we'll have to add support to optionally filter out cider.nrepl and refactor-nrepl in a similar way.