Pytak

- Fixes 12: Encrypted TLS Private Keys (Private Keys with Passphrases).
- Fixes 33: PyTAK Multicast read/write & write-only do not work on Windows.
- Fixes 40: Fix multicast binding on Windows.
- Fixes 48: Apply multicast membership to specified interface.
- Fixes 50: Add support for flow-tags.
- Fixes 51: CoT Time/Start/Stale timestamps aren't actually ISO-8601.
- Fixes 52: Add additional default CoT attributes.
- Fixes 53: Add generic CoT generation function.
- Various documentation fixes.

- Fixes 43: Add broadcast UDP support.
- Fixes 46: Move documentation from Sphinx to Markdown.
- Fixed 47: Change default constants to match config type hints (e.g. str instead of int).
- Updated Type Hints for function & method parameters.
- Updated Coverage for Python version work-arounds.
- Refactored `udp_client()` function, API unchanged.
- Fixed vague Exceptions.
- Renamed `cs2url()` to `connectString2url()`.

- Moved & expanded documentation at https://pytak.readthedocs.io/
- ``COT_URL`` now defaults to ``udp+wo://239.2.3.1:6969``, aka 'Mesh SA' in ATAK & WinTAK. This disables receiveing CoT by default. To enable receiving CoT, remove the ``+wo`` modifier.
* Fixes 31: 'protobuf support', "TAK Protocol, Version 1" is now the default output from PyTAK, *BUT* you must install the ``takproto`` python module seperately to ENABLE, otherwise reverts to CoT XML. PyTAK will automatically detect if the ``COT_URL`` is multicast or unicast, and use the appropriate protobuf format. See: https://github.com/snstac/takproto
* Fixes 36: 'Network is unreachable', added ``PYTAK_MULTICAST_LOCAL_ADDR`` to allow setting bind port on network connections.
* Fixes 37: 'unknown compression', reverted to github builder ubuntu-20.04
- Added support for reading PKCS12 (.p12) files containing public-private key pairs. Set p12 file with ``PYTAK_TLS_CLIENT_CERT``, and keystore password with ``PYTAK_TLS_CLIENT_PASSWORD``.
- Updates for AirTAK v1 support: https://www.snstac.com/blog/introducing-airtak-v1
- Moved setup.py metadata to setup.cfg
- Style, lint and layout cleanup of code.
- Added CI testing for Python 3.11
- Added Read The Docs builder.
- Added PyTAK shield logo & screenshots.

Exported `read_pref_package()` from client_functions.

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New Features:
- Made cryptography an install extras: You'll need this to use data packages! To install: `python3 -m pip install pytak[with_crypto]`
- Added write-only socket option to UDP sockets. Add `+wo` to the URL schema, as in: `udp+wo://239.2.3.1:6969`.

Bug Fixes:
- Fixed bad parsing of env var '%' characters on config import.

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New Features:
- Added multicast receive support.
- Added pref package / data package .zip support.

Other:
- Code cleanup.
- Documentation & README updates.
- 2023 copyright updates.
- Ramped up code coverage to at least 50% on most files.
- Added example of takproto support.