Adding initial source code of the GNOME Shell extension

This first non-functional prototype includes:
* Information about the user (logged in yes/no)
* GPII status, to turn the GPII on/off
* Authentication methods, to turn on/off:
** The USB Drive user listener
** The NFC Tag user listener
* Start using the GPII, to launch the PMT
* Adjust your current settings, to launch the PCP
* About, to open a webpage (remote or local) relevant information