shared: Add BuxtonControlMessage to notify_value

In buxton_wire_handle_response, with BuxtonControlMessage, the client
library handles notification registration seperately from other daemon
responses (still need to add handling for unnotify response). It will
check the response's status and if registration was successful, add
the notify_value to the notify_callbacks hashmap.
API: Add unsigned integer data types

Signed-off-by: William Douglas <william.douglas@intel.com>
core: Correct log message

Signed-off-by: William Douglas <william.douglas@intel.com>
core: unregister_notification returns notification msgid

When the daemon removes a client from notification list, the daemon
will send the message id for the notification to the client in its
response (to be used by the client to remove the callback from the
notification hashmap, not yet implemented).
shared: Remove message ID from notification callbacks

On unregister_notification, remove the message ID the daemon returns
from the notify_callbacks hashmap.

Signed-off-by: William Douglas <william.douglas@intel.com>