Clarify the Weaver documentation

- Explicitly mention that Weaver is for *persistent* storage
- Explicitly mention secure deletion requirement

Change-Id: I3eaf7408570ff20c69a21398e39e16be97d2a917
(cherry picked from commit acd066c61425d6b7f512445c6e2883baa28f381e)
Merged-In: I3eaf7408570ff20c69a21398e39e16be97d2a917
1 file changed