Support nested params

Add support nested params. For example:

```
/events?filter%5Bname%5D=sent+message

<%= active_link_to(_('Sent message'),
events_url(filter: { name: 'sent message' }),
class_active: 'current',
active: { filter: { name: 'sent message' } },
wrap_tag: :li ) %>
```

Start by locating the active_link_to helper and any existing tests for active link matching. Reproduce the nested filter URL from the example and trace how the active option is compared. Done means nested params such as filter[name] correctly mark the link as active, with coverage for the shown case.

Written by the indexing model from the issue text.