generalised all output and responses to user. Added json output options

bbcli/cli.py

bbcli/commands/announcements.py

bbcli/commands/assignments.py

bbcli/commands/contents.py

bbcli/commands/courses.py

bbcli/services/announcements_service.py

bbcli/services/assignment_service.py

bbcli/services/contents_service.py

bbcli/services/courses_service.py

bbcli/utils/utils.py

bbcli/views/announcements_view.py

bbcli/views/assignments_view.py

bbcli/views/contents_view.py

bbcli/views/course_view.py

bbcli/views/courses_view.py

tests/test_services/test_announcements_services.py

tests/test_services/test_assignments_services.py

tests/test_services/test_courses_services.py