Simplified Payload Option

[chughts]

Some nodes (STT, TTS, Conversation, Language Translator), need a simplified payload option. It should default to false, but when set, put the current payload onto msg.fullpayload, and msg.payload to a simplified version of the response that could be used to wire directly to the next node.

This would allow flows to be created that require fewer function nodes that set up msg.payload for the downstream nodes.

[chughts]

Implemented in STT and TTS in #300 Language Translator already had it.