The current design for Store classes (e.g. IMAP) did not provide for
any persistent storage. This is the beginning of a mechanism to
provide that. It's quite simplisitic - each Store can read/write one
persistent string - but that's enough for the first simple use case
(saving some sync data for EAS).
The core changes here - suggest reviewing first - are in Account.java,
Store.java, and AccountUnitTests.java. Everything else is just
following the API change that was necessary.
Note that, by definition, this only applies to remote stores (e.g.
IMAP, POP3). You'll see everywhere that LocalStore is passed null, and
this is correct - LocalStore *is* persistent storage and does not need
access (so far, at least).
BUG=1786939
Automated import of CL 146061
cd7e5664f9