Dub layout and iteration over struct

Sorry for three in one, if desired I can split it up and make a request with only those of interest.

* This uses the dub layout and package.json
* Bindings have been removed to use etc.c.sqlite3
* Iteration can be done over a struct

The last one allows for something like:
```
    auto data = db.query(SomeSqlQuery);
    foreach(record; data.range!DataStruct) { ... }

private struct DataStruct {
    Nullable!string value;
}
```