Usb device dettached state added to USB.H

A dettached state is needed for initial usb configuration
usb_init()
First usb initializer function

usb_init() added to USB.C
basic usb module configuring and enabling
Basic USB handlers added to USB.c

Each USB PIC interrupt has a handler function and
usb_handler() determines which handler has to be executed
First Example program created

Example.c contains main(), and defines the ISR (Interrupt Service Routine)
that calls the usb_handler() when the USB interrupt rise.
First Makefile

This Makefile compiles the example program (example.c) with the rest
of the usb implementation.
First README file created

Readme file contains a brief description of what this project is,
how to use it, how to understanding and autor information.

Is just a tentative and need to be completed!