Optimize OffsetRangeQuery

The Query implementation for OffsetRangeQuery is currently obviously correct, but less than optimal.

```rust
fn containing(&self, mut offset: u64, index: &LeafIndex, res: &mut [bool]) {
let range = offset..offset + index.keys.count();
// shortcut test
if !&self.0.intersects(&range) {
res.clear();
} else {
for i in 0..(index.keys.len()).min(res.len()) {
if res[i] {
res[i] = self.0.contains(&offset);
}
offset += 1;
}
}
}
```

Obviously this can be done more efficiently than checking every single offset.