Fixing OBO bug in results_in_batches
Add support for get_select_value operations

Example:

```ruby
NetSuite::Records::BaseRefList.get_select_value(
  field: 'class',
  recordType: 'salesOrder',
  sublist: 'itemList'
)
```
Treat @xsi:type as a RecordRef type
Minor code cleanup
Adding default namespace for easier manual calls
Some bug fixes and cleanup to the get_select_value implementation