Update IWear Logger with rpc control to start new log session

[yeshasvitirupachuri]

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Is your feature request related to a problem? Please describe.

The addition of new IWear Logger device is very handy in dumping wearable data form a wearable device to a .mat file. If I am not wrong the data dumping is continuous and multiple .mat files are created for the entire duration the yarprobotinterface is running. @prashanthr05 please correct me if I am wrong about this.

In some tests yesterday with the Paexo wearable device https://github.com/robotology/wearables/pull/117, we noticed this behaviour. So, for every new experiment we had to terminate the yarprobotinterface and start again for a new experiment.

Describe the solution you'd like

A nice additional feature that can improve the logging further is to have control over the logger to start a new acquisition through rpc control. This helps in logging multiple sessions that correspond to different experiments, without having to terminate and restart the wearable device through yarprobotinterface

CC @prashanthr05 @lrapetti