Initial commit of updated SMS Message Object
Fixed typo in Recipient_Phone_Number annotation
Added a few new fields and updated some annotations
Removed Subject field, as it was specific to MMS messages
Renamed Alphabet to Encoding to be more consistent with usage in other schemas
Updated annotation for Size field to state that it should be specified in bytes, not bits
Added boolean is_premium field
Added User_Data_Header field (of type HexBinaryObjectPropertyType)
Fixed typo in Size field in SMSMessageObjectType
Merge pull request #228 from ikiril01/issue_119

Added SMS Message Object