extend api to create an object by uploading the hashmap instead of actual data

extend api to create an object by uploading the hashmap instead of actual data

- enable format parameter in PUT requests on objects
- when format is json the api instead of actual data expects a json formatted dictionary (similar to one returned by extended GET responses) containing information about the block identities
- backend update_object_hashmap() now checks for the block existence before performing the update
- incase of missing data Conflict 409 is returned containing the list of the missing block identites