Default theme does not draw user attention for missed messages

In the default theme.json, message-new-instant events have a Sound action specified, and message-missed-instant events have a Led action specified. The same is true for message-new-sms/message-missed-sms.

These seem backwards, in that the message-missed- events are described as being used when a message is received "but not seen by the user." If the user did not see the message, they are most likely not able to see the notification LED either; a sound or vibration would be more appropriate to grab the user's attention. Conversely, when the user does see an incoming message, they likely do not need a sound to grab their attention.

See mms-stack-bugs#73 for a report from a user on how these defaults are confusing.

It's also possible that I've misunderstood in which cases these feedbackd events are supposed to be sent--I assume that an incoming message should only cause either a message-new-... or a message-missed-... event, not both. Is this true? The event naming spec could be more clear here.