Bluetooth: Add LE connect support

Bluetooth V4.0 adds support for Low Energy (LE) connections.
Specification introduces new set of hci commands to control LE
connection. This patch adds logic to create, cancel and disconnect
LE connections.

Signed-off-by: Ville Tervo <ville.tervo@nokia.com>
Acked-by: Marcel Holtmann <marcel@holtmann.org>
Signed-off-by: Gustavo F. Padovan <padovan@profusion.mobi>