Create skeleton for meta-arm layer

Add README and License Files in the root directory describing the layers
and process for interacting with the meta-arm layer.  Create the
directories for future layers (and add empty README files to force the
directories to be created by git).

Change-Id: I4d70759bf90b1c964e6d9040d145737b2f441205
Signed-off-by: Jon Mason <jon.mason@arm.com>