Remove code related to Pearson Testing Centers

cms/djangoapps/contentstore/tests/test_course_settings.py

common/djangoapps/external_auth/views.py

...on/djangoapps/student/management/commands/pearson_dump.py

...ngoapps/student/management/commands/pearson_export_cdd.py

...ngoapps/student/management/commands/pearson_export_ead.py

...ps/student/management/commands/pearson_import_conf_zip.py

...udent/management/commands/pearson_make_tc_registration.py

...oapps/student/management/commands/pearson_make_tc_user.py

...jangoapps/student/management/commands/pearson_transfer.py

.../djangoapps/student/management/commands/tests/__init__.py

...ngoapps/student/management/commands/tests/test_pearson.py

common/djangoapps/student/models.py

common/djangoapps/student/views.py

common/lib/xmodule/setup.py

common/lib/xmodule/xmodule/course_module.py

common/lib/xmodule/xmodule/modulestore/xml.py

common/lib/xmodule/xmodule/tests/rendering/__init__.py

...on/lib/xmodule/xmodule/tests/rendering/xmodule_asserts.py

common/lib/xmodule/xmodule/timelimit_module.py

common/lib/xmodule/xmodule/xml_module.py