Port Backend to SQLite/Sequelize (removes MongoDB), Support Electron (#14)

* 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

routes/api/webgrabber.js

@@ -1,7 +1,7 @@
 "use strict";
 
 var config = require('config');
-require('../../models/schema');
+require('../../models/db');
 
 var fs = require('fs');
 var phantom = require('node-phantom-simple');