Refactored SSL/Auth handling of Emails

[caronc]

Description:

Related issue (if applicable): #773 and apprise/discussion/760

Better handling of Email URLs:

• if ssl= is exclusively set to a secure method (such as ssl, or starttls), then it is implied that mailto:// should have been mailtos://
• Better handling of situations where an email is expected to be part of the login credentials and has already been specified as such. There were cases where the email login was incorrectly updated making authentication errors occur that shouldn't have otherwise been that way.
• The default SSL port assignment is automatically 465 when the mode=ssl (and not otherwise specified to be something different) and is 587 when mode=starttls. Prior to this PR, it always defaulted to 587 (the ssl mode was not considered).

Checklist

• The code change is tested and works locally.
• There is no commented out code in this PR.
• No lint errors (use flake8)
• 100% test coverage

Testing

Anyone can help test this source code as follows:

# Create a virtual environment to work in as follows:
python3 -m venv apprise

# Change into our new directory
cd apprise

# Activate our virtual environment
source bin/activate

# Install the branch
pip install git+https://github.com/caronc/apprise.git@773-improve-fastmail-support

# Test out the changes with the following command:
apprise -t "Test Title" -b "Test Message" \
  mailto://credentials