Add convenient "or" operator to queries

[raffomania]

This is currently kind of possible with regexes, but it would be nice to have something easier to use, for example commas: beet ls beatles, queen.

[sampsyo]

This would indeed be helpful. The plumbing is already there, in fact; just missing convenient syntax. See also #819.

[raffomania]

That's cool! I really like the idea of a comma. Nice alternatives I can think of are a pipe or a semicolon.

[sampsyo]

I like pipe too, but it has the disadvantage of needing escaping in most shells (as does semicolon). Comma does sidestep that!

[raffomania]

Good point. I'd vote for comma ;)

[sampsyo]

Done in #1423.