Change CREATE operations to UPDATE when SFID is available.

This update will check queue items that have been inserted
with a CREATE operation to see if they have already been
exported. This check is done by looking for a record in the
sync_map table. If a record with an SFID is found, the
operation is changed from CREATE to UPDATE and the SFID is
appended to the object.

This prevents duplicates from being created in Salesforce.
Merge pull request #373 from JacksonRiver/7.x-4.x-557_convert_creates_to_update_when_id

Change CREATE operations to UPDATE when SFID is available.