conn.py/dev.py: update documentation

To decrease the burdon of the first steps when reading the code base each file
now contains an overview of the classes and sections in the code files and each
section has a section header with a short intro sentence.

See GitHub Issue #72 for more details.

Signed-off-by: Erik Bernoth <erik.bernoth@gmail.com>
conn.py: debug; forgot a return

These returns are done for this case that a connection wants to return
something from their protected methods to the caller. In most cases they are
not used, but when you need it, then you are happy it is there.

Signed-off-by: Erik Bernoth <erik.bernoth@gmail.com>
conn.py: without login credentials return False

Signed-off-by: Erik Bernoth <erik.bernoth@gmail.com>
conn.py/dev.py: detail documentation

Both reviewers considered it too incomplete, therefore degree of detail was
increased for all documentation.

Signed-off-by: Erik Bernoth <erik.bernoth@gmail.com>
test_conn.py: test_fsm with second state check

Signed-off-by: Erik Bernoth <erik.bernoth@gmail.com>
test_conn.py: add error test case

Signed-off-by: Erik Bernoth <erik.bernoth@gmail.com>