secondary_ref lookup ergonmics

- secondary_ref is an odd name choice...perhaps `extra_indexes`, `alternate_indexes`, `lookups`?
- When you use a secondary_ref, the current syntax is

```ruby
# collection def
:secondary_refs = {:by_name => %i(name)}

# in parser
collection.lazy_find({:name => "foo"}, {:ref => :by_name})
```

A more ergnomic syntax would be

```ruby
collection.lazy_find(:by_name => {:name => "foo"})
```

Start with the parser handling collection.lazy_find and the existing secondary_ref declaration. Compare the current two-argument lookup form with the proposed single-argument form, then resolve the naming alternatives before defining the scope. Done means the API choice and migration behavior are agreed and documented in the relevant implementation and tests.

Written by the indexing model from the issue text.