Main update and modules small changes

Updated the main.py file so it distributes the tasks to the related
modules. Also added some comments.

In the rotary_encoder module, added functionality that the module keeps
a counter itself to see if a button is pressed once and the rotation is
once.

Added Rpi_receive and Rpi_send as examples for communication with the
Arduino to drive the stepper motor over the USB serial connection.
Display module

Added the display module