passing value of 1 for checkbox value
json_decoding custom properties when they are received from the edit form. now handling all custom property manipulation through getters and setters
removed unused saveTags function (might add this functionality later) and its call in afterSave. Changed custom_properties to private variable since this should be handled through getters and setters to keep track of its state (to serialize and unserialize into database)
refactored Session to be a static class. There is no need for this to have state