Demonstration of hardware and components use in ResourceManager

[destogl]

Here should be the first implementation of demo robots

The tasks are following:

• Create descriptions (Create descriptions for robots from examples #5)
• Add demo ResourceManager (Concept for loading the Robot using ResourceManager #14)
• Add all the missing Component types +(Add missing component types for the examples in the roadmap ros2_control#131 and Robot control components ros2_control#123)
• Create implementation of hardware defined in the roadmap example - see Do we need a FlexibleJointState message? roadmap#17
• Simple execution with read and writes calls to components and the hardware

[destogl]

After ros-controls/ros2_control#121 and ros-controls/ros2_control#127 there are many conceptual changes. Therefore, closing this in favor of a new clean PR