fix annotation import in model classes and add additional json properties in article listing response.
add article request class
add article activity and article list view row layout xml files.
update properties and strings resource files and remove removed resource from main.xml file.
remove unused imports in subcategorylistingarrayadapter class.
add articlelistingarrayadapter class.
removed unused imports and codes from categoryfragment class.
add new activity - articleactivity class and define the activity in android manifest file.