fix session token/cookie handling for arbitrary server IPs; fix realtime update distribution via websockets

* 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

update vulnerable moment package

WIP Importer for spacedeck.com exports
Alternative (to S3) local file storage
Alternative mocked redis (run without redis for single process instances)
Experimental Docker support

# Conflicts:
#	README.md