New style

* New unified background color for the entire application
* New launcher icon
* New action
* New settings icon
* New style Navigation Drawer

Signed-off-by: AlvaroOrduna <alvaro.orduna.92@gmail.com>
MainActivity: Introduce the user to the drawer at first use

At first use, show the navigation drawer automatically to help
the user learn the functionality and structure of the app.

Signed-off-by: AlvaroOrduna <alvaro.orduna.92@gmail.com>