Basic implementation of gui.dataview.DataTabWidget missing

A basic implementation of the DataTabWidget needs to be added. Only the skeleton / an empty class is enough. Remember to add the respective attributes to the using classes.

Requires: Basic implementation of gui.dataview.AbstractDa... (#18 - closed), Basic implementation of gui.dataview.NetworkSta... (#16 - closed), Implement: PlotData + AttrType (#26 - closed)