Moved sync.strategy to folder.sync.filter.

Changed location of the synchronization data from $XDG_DATA_HOME/himalaya/<account-name> to $XDG_DATA_HOME/pimalaya/email/sync/<account-name>-cache.

Changed location of the synchronization cache from sync.dir to $XDG_CACHE_HOME/pimalaya/email/sync/<hash>/.

Replaced id mapping database SQLite by sled, a pure key-val store written in Rust to improve portability of the tool. Therefore, id aliases are reset.

Improved pre and post edit choices interaction [#58].

Improved account synchronization performances, making it 50% faster than mbsync and 370% faster than OfflineIMAP.

Changed envelope.watch.{event}.{hook}: hooks can now be cumulated. For example it is possible to send a system notification and execute a shell command when receiving a new envelope:

envelope.watch.received.notify.summary = "New message from {sender}"
envelope.watch.received.notify.body = "{subject}"
envelope.watch.received.cmd = "echo {id} >> /tmp/new-email-counter"