fixes for marshalling/unmarshalling issues

These two are issues with aws sdk 1.5.1 and tested against 1.5.1 version. I don't know whether they are issues with 1.4.x or not.

1. the batch get result issue. The json generated from BatchGetItemResultMarshaller.java	doesn't match live dynamodb result format and caused wrong unmarshalling result.

2. query result unmarshalling issue. This is a very weird issue. The json data format generated from QueryResultMarshaller.java is the same as the one from live dynamodb. However, the one has ConsumedCapacity in front of items. This difference caused sdk 1.5.1 wrongly deserializes ConsumedCapacity object into a invalid result item. It works after the sequence is changed in this fix.  I didn't have time to dig more in sdk 1.5.1