Add various options: mark as read, timezone, SSL certificate verification

Added a few extra options:

**Mark as read** - if disabled, emails will not be marked as read when notifying. To prevent notifications being triggered every time the server is polled, an array of message IDs is stored for the session listing emails that have already been notified.
**Timezone** - self explanatory
**SSL certificate verification** - disable SSL certificate warnings if the server you are using uses an invalid certificate for whatever reason.