user-manual-meta: Added the layers content from the YP manual.

Copied the Layers content from the Common Tasks section of the
YP Dev Manual.

Signed-off-by: Bill Traynor <wmat@alphatroop.com>
user-manual-meta: Commented out unfinished bits for now.

Commented out the Task Checksums and Setscene section for now.

Signed-off-by: Bill Traynor <wmat@alphatroop.com>