This adds support for anonymously connecting to SMTP servers
that do not require authentication; if a username is not provided,
it will not attempt to authenticate.
* The MongoDB/Mongoose data storage is removed in favor of Sequelize. This abstracts over SQLite or RDBMs like PostgreSQL and MSSQL. The default is SQLite, which significantly simplifies deployments in end-user environments.
* As Spacedeck now has no more mandatory server dependencies, we can wrap it in Electron and ship it as a desktop application.
* Removes docker-compose.yml
* First version of import UI
