Add README file
Add AUTHORS file
ll: Add link layer initial files

This patch adds the initial Bluetooth Low Energy Link Layer files which
it is planned to manage the radio layer, controlling packets
transmission and state machines.
bci: Add Bluetooth Command Interface files

This patch adds the initial files to implement the Bluetooth Low Energy
Command Interface. It is planned to similar to HCI interface, however it
might provide less abstractions since there isn't host and controller
separation on embedded systems.