Federated search

## ToDo

- [x] Implement iQvoc-to-iQvoc search adaptor class
- [x] Instantiate adaptor instances from configuration
- [x] Iterate over adaptor instances (remotes) when searching, aggregate results
- [x] Extend search form (allow for selecting remotes)
- [x] VoID integration

## Gotchas

- [x] Interface-bound localization
- [x] Pagination
- [x] Parameter names for classes