This patch also adds a non-rendered license and copyright header to the
top-level README, and applies the same rendering-exclusion to the headers of the
README files provided within each layer sub-directory.

Issue-Id: SCM-4394
Signed-off-by: Richard Neill <richard.neill@arm.com>
Change-Id: Id7e171b8f8e373bff5e23555c6e719942f83e636