implement `__main__.py` enty points

[Cube707]

This PR implements entripoints via __main__.py files, which closes #407. This can replace the existing bin/snap7-server.py script and offer a much more pythonic way to achive the same.

Currently implemented:

Usage: python -m snap7.server [OPTIONS]

  Command entrypoint to start a dummy server.

Options:
  -p, --port INTEGER  Port the server will listen on.
  --dll FILE          Path to the snap7 DLL (if it is not on path).
  --help              Show this message and exit.

Diskussion

There are still a few question I feel should be discussed:

• do we also want setuptools to create a snap7-server binary on install?
• with the current commits, python -m snap7.client could be implemented in the future as well. This could be a simple CLI offering terminal acces to some basic versions of the functions this project provides. (for example: snap7.client db-read 0 --start 120 --size 1, etc...)
• is click acceptable as a dependency. This makes extending the CLI much simpler (espacially if snap7.client will be implementd). But the current, simple behaviour could be implemented without this dependency.
• Should bin/snap7-server.py be removed right now or keep around for backwards compatibily?
• The server.mainloop and server._init_standard_values functions fit much better into the __main__.py file, but this would break the API, so is probably not desirable. We could however move the implmentaion and import them back into server if that is acceptable
• are there more features the snap7.server should have?
  Ideas:
  • option to pass the IP-interface to bind to
  • option to toggle/pass initalization values (probalby stupid, have them run their own script for that)
  • --version
  • --verbose/-v

---

tests are not working right now...

keeping this a draft untill discussion is done

[Cube707]

@gijzelaerr could you take a look at this?

[Cube707]

Implemented the changes.

Current behavior:

Usage: python -m snap7.server [OPTIONS]
# or
Usage: snap7-server [OPTIONS]

  Start a S7 dummy server with some default values.

Options:
  -p, --port INTEGER  Port the server will listen on.
  -v, --verbose       Also print debug-output.
  --version           Show the version and exit.
  -h, --help          Show this message and exit.

[Hidden option: ]
  --dll PATH

I now fully removed the old script. It would cause name-collisions with the new entry-point. The new entry-point is a drop-in replacement. Only preople who provieded a first argument (the path to the dll) to the old script will get an Error: Got unexpected extra argument (foo)

[gijzelaerr]

there seems to be a conflict with master.

[Cube707]

rebased, should merge now

[Cube707]

@gijzelaerr should be ready

[gijzelaerr]

i think i've fixed master, if you merge master into your branch the build should work

[Cube707]

@gijzelaerr I rebase onto the new state of master and now all tests pass. Great work fixing the workflows