Add missing __init__.py files & let setup.py find all importable packages on its own

[da-h]

Description

In the recent refactoring in #858 I've missed to tell setup.py about the new python directories.
This results in visdom to be effectively broken when installed from pip or setup.py.

The solution is quite easy:

• adding all missing __init__.py files
• tell setup.py about the new directories. I have solved this by using the automatic setuptools.find_packages method.

This should also solve #878, who has pointed out the error.

How Has This Been Tested?

Running locally python setup.py install --user works now as expected.

Note

Maybe it would be best to install visdom using setup.py for all tests so this does not happen again?

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Code refactor or cleanup (changes to existing code for improved readability or performance)

Checklist:

• I adapted the version number under py/visdom/VERSION according to Semantic Versioning
  A nothing has changed really, I added a .post1 to the version.
• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.

[JackUrb]

The visual regression test is failing as we need to update that to no longer reference server.py. We should do a check to see if that string exists anywhere in the codebase before merging.

[da-h]

Thx for looking into this. I have submitted a PR (#880) to fix this error.

Also, regarding all the warnings below recent github-actions, it seems there are some more things to be done to modernize workflows to newer github apis.
I will submit a separate PR to tackle the warnings soon.