Changes to make it work in raspbian

[DanielSSilva]

I've made the following changes:

• rename the project from Rpi to RPi to be consistent with the rest;
• Created a library that has what's common between both Demo projects;
• Simplified the Demo for Core, so that you don't need to re-compile each time you want to test a new feature (although you have to stop and start the program)

Things will brake on the UWP project, because I cannot compile it (I'm on a linux machine)

Also, is there any chance you can update the nuget package so that it includes the changes?

[DanielSSilva]

Also, on the compass example, you use a "Point" class. The one that exists that has that same point is on "using System.Drawing;", which does not allow to have doubles, so I've rounded it to int