Update IWear Logger with rpc control to start new log session

**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

Start by locating the IWear Logger component and its RPC control entry point, then inspect how yarprobotinterface currently creates .mat files and handles continuous logging. Done means a new acquisition can be started through RPC without restarting yarprobotinterface, with separate sessions producing separate log files.

Written by the indexing model from the issue text.