Mumailer

- Added main script which includes both profiles and command line options

- Added compatibility with Python 3.11
- Added encryption protocol TLS for latest TLS version
- Renamed Message method to_email_message to _to_email_message
- Removed unused Attachment charset
- Allowed also no encryption
- Removed use_ssl and use_tls and determine the connection type and TLS encryption from the encryption method

- Code cleanup

- Updated dependencies
- Code cleanup
- Added icons

- Fixed typo in the documentation

- Added custom headers to the Message