DIscover and print all information

[ffries]

According to feature https://github.com/brendan-w/python-OBD/issues/82

This patch adds a print_discovered() clause which prints all detailed information about a connection. It can simply be triggered using:

import obd
connection = obd.OBD()
connection.print_discovered()

It also modified some functions with the prefix "get_" for clarity and updates testing accordingly.

Feel free to modify, but we probably need some kind of utility to help and debug users.

[ffries]

An option would be to write a simpler discover_and_exit() clause, which would auto-connect, discover, print OBD available commands and exit.