Merge branch 'rocksdb' into 'next'

Cargo.lock

Cargo.toml

conduit-example.toml

src/client_server/context.rs

src/client_server/device.rs

src/client_server/filter.rs

src/client_server/message.rs

src/client_server/sync.rs

src/database.rs

src/database/abstraction.rs

src/database/abstraction/rocksdb.rs

src/database/abstraction/sqlite.rs

src/database/abstraction/watchers.rs

src/database/admin.rs

src/database/rooms.rs

src/database/users.rs

src/error.rs

src/server_server.rs