BREAKING CHANGE: More complete SSL / TLS settings

This commit does a few things:
* Rewrites the file to be in alphabetical order for easy browsing
* Adds an "alias" feature to reduce settings duplication - we were
having some issues where e.g. one version of iCloud had the correct
settings and some other versions did not, resulting in very confusing
support engagements.
* Audits all settings & upgrades settings that were using plaintext
connections to use encrypted connections whenever possible
* Adds support for specifying IMAP & SMTP TLS settings separately, and
also in a more specific way. The previous, ambiguous "ssl" setting
has been replaced with "imap_security" and "smtp_security", which have
the possible values "SSL / TLS", "STARTTLS", or "none". Providers can
also specify the boolean key "imap_allow_insecure_ssl" or
"smtp_allow_insecure_ssl" if insecure ciphers such as SSLv3 are required
to connect.
* Removes the 'occurrences' field, which I could find no reference to in
our codebase.

Author: spang