Better logging on unhandled exceptions

[TwitchBronBron]

Many times we have unhandled exceptions in promise flows that get suppressed by the promises library. For example:

• wrong parameter data type for .then callback
• runtime exception in a callback (like divide by zero)
• intentional throw

We need better logging around these situations to help developers know when their promise flows haven't been properly handled.

Perhaps a conditional compile constant that enables this logging?