The object must be cleaned up before storing in DB, because some code
(out of rcube_message and rcube_imap classes) is changing objects data
e.g. parts mimetype or body. Now it's become a problem because we're
saving the object in cache at shutdown (after all modifications).
- Make stored message object smaller by removing some redundant data.
Indexes are stored in a separate table, so there's no need to store all messages in a folder
Added threads data caching
Flags are stored separately, so flag change doesn't cause DELETE+INSERT, just UPDATE
- Partial QRESYNC support
- Improved FETCH response handling
- Improvements in response tokenization method
