Fix incorrect __repr__ of NetworkDevice ports
Revise layout of import statements

From  PEP8:

"Imports are always put at the top of the file, just after any module
comments and docstrings, and before module globals and constants.

Imports should be grouped in the following order:

1. standard library imports
2. related third party imports
3. local application/library specific imports

You should put a blank line between each group of imports."
Do not use wildcard imports

From PEP8:

"Wildcard imports (from <module> import *) should be avoided, as they
make it unclear which names are present in the namespace, confusing both
readers and many automated tools."
Add blank line at the end of docstrings
Merge branch 'make-code-comply-with-pep8-style' into next
Invoke pylint from Makefile
Makefile: invoke pylint only for the files in the package ft4fttsim
Revise import statements

- Delete unused imports.
- Put imports at the top of each corresponding module.
Add docstring for simlogging module
simlogging.py: changes to silence pylint complaints
simlogging.py: Add a leading underscore to some attribute names
Do not use empty dictionary as default parameter value

This is the same issue as in commit 7a35bbde4cfafbff40e66c67d5a892774038b0e0
Add docstring to networking module
Add and revise docstrings
Remove setter for _Sublink.{transmitter,receiver}_port properties

These property should only be set through the constructor of class _Sublink.
Eliminate classes Port.InputQueue and Port.OutputQueue

We now use simpy.Store instances directly.
Define ethernet constants in a separate module
Delete unused attribute device of class Port
Add missing docstrings to networking module
Rename a few variables and other minor refactorings