Add option to be able to filter ADS or (!INSPIRE).

[duetosymmetry]

This adds a cli option and the python code which enables it. Currently there are only two filter types available:

• "ads" which is the old behavior
• "all" which is all bibkeys that do not look like INSPIRE keys
  I imagine others might want to implement their own filter types, or we can allow regexes on the commandline. The latter would require again changing the cli behavior, because we would want another string input aside from the Choice "regex" or similar.

[matthewfeickert]

I'm going to rebase this against master real quick so that it doesn't have a repeat commit.

[matthewfeickert]

Looks good code wise, though maybe worth adding an example of the new CLI feature to the README? I'll approve this though as the code seems fine.

[duetosymmetry]

Sorry about the double commit! I forgot to back up to master before checking out a new feature branch. Good idea about the extra documentation.

[matthewfeickert]

Sorry about the double commit! I forgot to back up to master before checking out a new feature branch.

Oh no, nothing to be sorry about! We do this all the time on pyhf, but we just are in the habit of rebasing our feature branches off of the current state of master.