front: Minor cleanup of DiagnosticActivity.

Changed some function names for clarity, shuffled some lines of code.
Getting the abstracted hardware id instead of what the O/S gives us
(currently equivalent, but possibly not in the future).
front: PromptInputCode cleans up listeners and is a bit more general.

Previously, clients never heard when the user clicked cancel, which is
important if the client needs to cleanup after the dialog closes.
front: Added missing OUYA check before vibration.
doc: Updated changelog.
front: Add more info to Help dialog, popup after install/update.

These are currently the most common support issues.  I think most
people never even explore the plugins menu, let alone realize it might
solve some of their issues.

The popup after install/update might reduce the number of knee-jerk
bad reviews on the play store.