add options to create store manager for iCloud.

How to setup:

```
      sm = CDQStoreManager.new(iCloud:true, container: "blah") # usually you don't need the container option.
      CDQ.cdq.setup(stores:sm)
```

First I tried like this:

```
    CDQ.cdq.setup(store:sm.current)
```

But it generates CDQStoreManager twice.
Then I add :stores option to setup.