GC-47: Add support for Python 3.13:

- Simplify the option presence checks in functional tests to avoid
having to deal with differences in output between Python 3.13 and
older versions (similar checks are already in place for things like
key specification anyway). For more details, see this commit:

https://github.com/python/cpython/commit/c4a2e8a2c5188c3288d57b80852e92c83f46f6f3

GC-44: Added support for Python 3.12:

- Updated documentation.
- Updated release notes.
- Updated supported Python versions in package configuration file.
- Updated Python versions used for tests.

GC-43: Added support for Python 3.11:

- Updated documentation.
- Updated release notes.
- Updated supported Python versions in package configuration file.
- Updated Python versions used for tests.

GC-42: Added support for Python 3.10:

- Updated documentation.
- Updated release notes.
- Updated functional tests (small tweak for help output change).
- Added signing key for the Python 3.10 and 3.11 releases.
- Updated supported Python versions in package configuration file.
- Updated Python versions used for tests.

GC-45: Update copyright information:

- Changes to code base were previously done in 2020 as well (based on
git history).

GC-45: Drop support for Python 3.5, 3.6, and 3.7:

- Updated documentation, removing references to versions as being
supported.
- Switched the Vagrant test machine to Debian Bullseye (still in LTS
support) to match the main development environment.
- Updated functional tests for output changes in OpenSSL CLI from
Debian Bullseye.
- Updated Tox configuration and instructions.
- Dropped workaround for Python 3.5.
- Updated package requirements.
- Updated release notes.

GC-39: Added support for Python 3.9:

- Updated release notes
- Updated functional test for changes in help output in Python 3.9.
- Updated comments on public signing keys used for validating the
Python archives when using Vagrant provisioning.
- Updated supported Python versions in package configuration file.
- Updated Python versions used for tests.

GC-33: Added support for Python 3.8:

- Updated release notes.
- Updated documentation.
- Updated Python versions used for tests.
- Updated supported Python versions in package configuration file.

GC-35: Drop support for Python 3.4:

- Updated documentation, removing Python 3.4 as supported version.
- Updated documentation to include support for Python 3.7 (this was
already supported, but documentation did not list it in a couple of
places).
- Updated Tox configuration with list of supported Python
versions.
- Build Python 3.5.x for full test against all Python versions in
order to make it independent of underlying distribution Python
version.
- Update package requirements.
- Updated release notes.

Noticket: Small improvements to documentation:

- List supported Python versions a bit more explicitly (improves
readibility/stands out better).
- Use dashes instead of asterisks for lists of items (just a syntax
change).
- Added link to documentation (RTD) to README file.

GC-16: Added user documentation for the client command:

- Updated the features entry in README file, adding some missing
information about other features implemented as well.
- Added quick usage instruction for issuing a client certificate.
- Added the client certificate artifacts directory to listing of
directories used.
- Added expanded usage instructions for the client command.
- Fixed some invalid invocation example for the server command.

GC-2: Adding initial documentation skeleton with some basic information about the project:

- Added basic documentation describing the project.
- Updated gitignore file to ensure documentation build artifacts stay
out of the repository.
- README file placed at top directory for convenient access.