Add throttling of AppleScript requests

[SphtKr]

It is apparently possible for the system to get backed up with too many AppleScript requests to where they just keep piling on. Some work has already been done for this (not yet in master at the present moment), adding a queue and an option to change the polling interval. Nevertheless if the system is under other stress this may happen.

Implement a throttling mechanism where if the queue gets too deep it will temporarily reduce the polling interval until the queue empties.