Add ros_publish test + external interface.

CMakeLists.txt

tests/CMakeLists.txt

tests/impl_test_sot_external_interface.cpp

tests/impl_test_sot_external_interface.hh

tests/impl_test_sot_mock_device.cpp

tests/impl_test_sot_mock_device.hh

tests/python_scripts/simple_ros_publish.py

tests/test_ros_interpreter.cpp

tests/test_sot_loader.cpp