Bug 985415: Fix console output for NFC notification commands

This patch adds well-formed error messages to the notification
commands of NFC. Each message is prefixed by 'KO', which signals
an error to the emulator.

Signed-off-by: Thomas Zimmermann <tdz@users.sourceforge.net>
Bug 985415: Rework console interface for NFC notifications

This patch improves the console interface for generating NFC
notifications. The creator functions now return -1 on errors,
and the use of a non-existing active RE or notification type
is detected. Each of these problems produces a well-formed
error message.

Signed-off-by: Thomas Zimmermann <tdz@users.sourceforge.net>