No way to do non-inplace operations without operators

[Nemo157]

let rb1 = RoaringBitmap::from_iter(0..1u32);
let rb2 = RoaringBitmap::from_iter(2..3u32);
let rb3 = &rb1 | &rb2;

No way to do the above using an inherent method on rb1, might be worth adding something like let rb3 = rb1.or_into_a_new_bitmap(rb2); (and for the other operators).