* Implements Status Folder format v2, with a mechanism to upgrade an
old statusfolder.
* Do not warn about Gmail and GmailMaildir needing sqlite backend
anymore.
* Clean repository.LocalStatus reusing some code from
folder.LocalStatus.
* Change field separator in the plaintext file from ':' to '|'. Now
the local status stores gmail labels. If they contain field
separator character (formerly ':'), they get messed up. The new
character '|' is less likely to appear in a label.
Signed-off-by: Eygene Ryabinkin <rea@codelabs.ru>
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