Enable Voice Mail for screened and permitted callers

[emxsys]

Add voice messaging capabilities and options for all callers:

• Add options to enable voice mail for permitted and screen callers
• Configure answer after n number of rings
• Add button(s) to reset the "unplayed" status of a voice message

FYI: In North America, the standard ring cadence is "2-4", or two seconds of ringing followed by four seconds of silence (33% Duty Cycle). This information could be used to implement a time-based wait system before pickup. E.g., to wait for for n rings would be time.sleep( n * 6)

Examples:

• 'Screened' calls could be intercepted with the general greeting and then sent to voice mail
• 'Permitted' calls could ring n times, allowing you to answer, before being sent to voice mail