Introduce the Signal block

[GiulioRomualdi]

I noticed that every time I need to read the data from a yarp port, I always need the following ingredients

yarp::os::BufferedPort<T> port; 
U data; /**< Vector containing the data. */
std::unique_ptr<Smoother> smoother; 
std::mutex mutex // <---- Useful if we are going to introduce threads in the final application 

Where the Smoother is an optional class that smooths the data. In general, it is a low pass filter or a minimum jerk trajectory generator.

Last but not least, a signal may be streamed not only through a yarp port. For instance, the signal may arrive from a file (i.e. @prashanthr05 dataset for testing the estimation)

We can try to abstract the concept of the signal and introduce an interface for streaming data through the network/logfile.

A possible idea is to adapt what @xenvre did in robots-io.

[traversaro]

For reference, this is also similar to the YARPRead block available in WB-Toolbox:

• https://github.com/robotology/wb-toolbox/blob/v5/toolbox/library/src/YarpRead.cpp

[traversaro]

Also Drake's LCM systems are related (they also include a system to playback logs):

• https://github.com/RobotLocomotion/drake/tree/master/systems/lcm