Create a generic node container

[wjwwood]

This is a spin-off from: ros2/ros2#55

We need a generic program which can be run and then remotely instructed to load and execute a node.

This program should probably:

• Allow configuration of the internal executor.
• Provide ROS Services for loading and running a node.

This is not really useful until we have the ability to make, find, and dynamically load nodes, see:

• Provide CMake infrastructure for creating a node #114
• make producer / consumer plugins in a shared library and load them with pluginlib demos#18

This is also blocked by decisions that need to be made in: #48

[Karsten1987]

@wjwwood Can this be closed given that we have the composition demos?

[wjwwood]

No, the demo just demonstrates the technology, it doesn’t provide a general purpose executable that people can rely on going forward. It wouldn’t be a good idea for people to build robot launch files that launch critical executables from a demo package.

[rotu]

@wjwwood How about now that rclcpp_components component_container exists?

[ZhenshengLee]

Canbe closed? @wjwwood

[mjcarroll]

Yes, I think we are good here.