IMAP extension support

DoD: Extension is considered to be supported if it is advertised, usable by clients and integration tests for its use exist.

## IMAP4rev2

Extensions that are required to be compatible with IMAP4rev2 specification.

- [ ] LITERAL+
- [ ] NAMESPACE
- [ ] UIDPLUS
- [ ] ESEARCH
- [ ] SEARCHRES
- [ ] LIST-EXTENDED
- [ ] LIST-STATUS
- [x] MOVE (tested via imaptest)
- [ ] SASL-IR
- [ ] ENABLE
- [ ] UNSELECT
- [ ] IDLE

## Recommended for IMAP4rev2

Extensions that were removed from IMAP4rev2 but are still recommended. Widely supported and used by clients.

- [ ] CONDSTORE
- [ ] QRESYNC
- [ ] OBJECTID

## "Lemonade" Profile

Extensions set from 2006 recommended for efficient operation of mobile clients ("to Support Diverse Service Environments").

- [ ] COMPRESS=DEFLATE
- [ ] I18NLEVEL=1/2
- [ ] SORT
- [ ] CONVERT
- [ ] CONTEXT=SEARCH
- [ ] CONTEXT=SORT
- [ ] ESORT
- [ ] METADATA-SERVER
- [ ] METADATA
- [ ] NOTIFY
- [ ] FILTERS
- [ ] URLAUTH=BINARY
- [ ] URLAUTH
- [ ] URL-PARTIAL
- [ ] LITERAL+

## Misc

- [ ] MULTISEARCH
- [ ] WITHIN
- [ ] APPENDLIMIT (#11)
- [ ] QUOTA (#11)
- [ ] CHILDREN
- [ ] THREAD=ORDEREDSUBJECT (#8)
- [ ] THREAD=REFERENCES (#8)
- [ ] BINARY
- [ ] ACL (to expose access information for shared mailboxes)

## Modern IMAP

Experimental extensions that bring considerable improvements.

- [ ] UIDONLY
- [ ] PARTIAL
- [ ] PREVIEW
- [ ] INPROGRESS
- [ ] SEARCH=FUZZY