Expose ROS features in Python interface

[marip8]

Per #15 we should create a small reach_ros Python interface to expose various features of the ROS interface to a Python script. This should include:

• Initializing rclcpp with argv

  def init_ros(argv=None):

• Declaring/setting/getting ROS parameters in the singleton node

  def get_parameter(name: str) -> object:
  def set_parameter(name: str, val: object) -> None:
  def declare_parameter(name: str, default: object) -> None:

Let's start using boost::python as in reach. We may have to make a few modifications to reach to export relevant binding header files (like utils.hpp) though.