Favor options object instead of arguments list in method signatures

Instead of :

```
SQL.execute(sql [,vars][, options][, callback])
```

Use :

```
SQL.execute(sql, options);
SQL.execute(sql, {
   vars: vars
   callback: callback
})
```

Pros : 
- doesn't force the user to specify all args if they only need the last one
- changes/adds to the API are a no brainer
- easy set up of defaults in the beginning of the function
