Add images task model

*Add images task model
*Removed redundant serialization of tasks in Task class
*Removed dictionary creation in Result class that was not needed
*Corrected xml error message formatting
*Removed extra blank lines
*Removed __init__ from Tasks class
*Updated _dict_to_obj methods
*Added super constructor calls
*Added checks for input and result being none

Change-Id: I2b550707d8a95d8d5449702852142a0609ffede0