title: Best way to make a project with multiple files
body: <p>I am developing Arduino based system that will enlarge over time. At the moment it has only the humidity and temperature read functionality. But soon a door control, sound recording and gsm web client support will be added. I want all these to be included as libraries and used in the main part. I'm thinking of one ino file that includes all other modules and calls their functions. My question is what is the best and most clean way to do it?</p>