Ibeam

Major:
* Switched from chrome to chromium webdriver
* Added ARM64 support (fantastic contribution from maksimstojkovic in 31 👏)
* Tested on AMD64 Windows PC and ARM64 Ubuntu 20.04.2 Server 64-bit RPi4
* Currently does not support ARMHF due to cryptography rust dependencies
* Added multi-platform build instructions
* Added reauthentication
* Not killing gateway after logout, instead now parsing tickle data for 'competing' flag and reauthenticating if found
* Reordered Docker layers to reduce consecutive build times
* Made 'Invalid username password combination' count towards MAX_FAILED_AUTH
* Added critical failure and shutdown on no 2FA handler provided when it's needed
* Added retries to Google2faHandler marking the message as read
* Added handling of ibkey promo (fantastic contribution from JackD111 in 69 🥳)

Misc:

* Added log when found a custom conf.yaml
* Made logging format customisable through LOG_FORMAT env var
* Removed unused `invoke` build requirements
* Added a warning about 'Open https://localhost:5000 to login'
* Changed BlockingScheduler to BackgroundScheduler and support for keyboard interrupt

Thank you to everyone who contributed in the discussions, reported problems, contacted IBKR and helped build this tool 👍 Great job everyone!

* refactored and broken down the `gateway_client` to:
* `http_handler` - for HTTP requests to the Gateway
* `authenticate` - for authenticating using the Gateway's webpage
* `inputs_handler` - for handling Inputs Directory
* `var` - for environment variables
* `process_utils` - for starting the gateway

As a result `gateway_client` is more of a logic manager that utilises these various modules/classes

* added 2FA handling - executed through `TwoFaHandler` child classes
* User can specify which handler to use by setting IBEAM_TWO_FA_HANDLER env var. Accepted values are 'GOOGLE_MSG', 'EXTERNAL_REQUEST' and 'CUSTOM_HANDLER'. These correspond to the following:
* TwoFaHandlers available:
* `GoogleMessageTwoFaHandler` - using Google Messages, written originally by gmcmicken - I added some small tweaks
* `ExternalRequestTwoFaHandler` - calling an external URL for the 2FA code
* custom handler - allowing users to provide a custom handler through the Inputs Directory
* tweaked some logging messages to be more accurate and moved logs' logic to a separate module
* updated the authentication logic to make it more reliable and provide more failsafes
* added `support/verify_connection.py` script for testing the connection and certificates
* updated the wikipedia to reflect and document all of these changes

* Added handling for '[Errno 111] Connection refused' - treating it as Gateway running but not serving yet.

- added `IBEAM_REQUEST_RETRIES` env var used during maintenance to determine how many times should IBeam attempt to communicate with the Gateway before attempting reauthentication
- added `IBEAM_REQUEST_TIMEOUT` env var defining the timeout for requests to the Gateway in seconds.
- added `IBEAM_OAUTH_TIMEOUT` env var defining the timeout for login.
- now uses tickle to verify authentication and extend sessions, instead of validate
- now checks for authentication status apart from successful requests
- deprecated `-l`/`--validate` standalone argument
- added `-c` / `--check` standalone argument to check if Gateway's session is authenticated