Mmpy-bot

WARNING: This version breaks backward compatibility with plugins written for 1.x versions of mmpy_bot

Completely new codebase written to take advantage of [mattermostdriver](https://pypi.org/project/mattermostdriver/) adding the following features:
- Multi-threading and asyncio execution
- Integrated webhook server
- Support for click functions
- Job scheduling
- Compatible with Python 3.8+ only

Quickfix for PyPi.org package issues.

Long-awaited release to PyPi.org with latest changes:

Enhancements
- Run tests against a mattermost instance running in docker (150) [rwky]
- Adding feature to remove reactions (101) [attzonko]
- Introduce at_start (135) [unode]
- enable loading single module plugins (95) [seLain]

Bug fixes
- Fix scheduler.once() trigger_time default value (141) [unode]
- Add missing return statements to message methods (134) [Crocmagnon]
- Remove '' from sender_name (119) (120) [sheiun]
- Fix api-call in update_post (105) [3mb3dw0rk5]
- reply_thread add message in existing thread if present (104) [petrus-v]
- Fix message.update() (103) [knedlsepp]
- Changing allowed channels functionality to ignore direct messages (98) [attzonko]
- Updating message.comment() to use message.reply_thread() (97) [attzonko]

Thank you all for your patience and contributions!

Enhancements
- Adding new decorator allowed_channels (88) [attzonko]
- Adding reply_thread to message api (90) [attzonko]

Bug fixes
- Fixing bug with decorators and help. (87) [attzonko]
- Made requirements come from a single point of truth (85) [attzonko]

Bug Fixes
- Fix requirements to include schedule

Enhancements
- Added ability to allow users to specify explicit webhook id (66)
- Added ability to pass additional properties to regular messages (72)

Bug Fixes
- Fail to start Bot if settings contain non-ASCII characters (71)
- Incorrect message sending behavior by webhook (74)
- Index out of bound for `v= __main__` (77)
- Handling socket.error (79)
- Added expression to explicity match 'ping' (81)