Bluetooth: Add support for communicating keys with userspace

As the key format has changed to something that has a dynamic size,
the way that keys are received and sent must be changed.

The structure fields order is changed to make the parsing of the
information received from the Management Interface easier.

Signed-off-by: Vinicius Costa Gomes <vinicius.gomes@openbossa.org>
Signed-off-by: Gustavo F. Padovan <padovan@profusion.mobi>