Docs: Update sign_builds.jd

Add a new "release-keys" section and provide easy recipes for signing
flashable images and OTAs.  Reorganize the document to put the most widely
used information at the top, and move advanced topics into "appendices."
Explain the pitfalls of shipping images built with test-keys.

Bug: 21365053
Change-Id: I696591abd5b54d9e9d56bc15bcf198951a338d18
Signed-off-by: Kevin Cernekee <cernekee@google.com>
1 file changed