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/space_digest.js

@@ -1,17 +1,15 @@
 "use strict";
 
 var config = require('config');
-require('../../models/schema');
+require('../../models/db');
 
 var async = require('async');
 var fs = require('fs');
 var _ = require("underscore");
-var mongoose = require("mongoose");
 var request = require('request');
 var url = require("url");
 var path = require("path");
 var crypto = require('crypto');
-var qr = require('qr-image');
 var glob = require('glob');
 var gm = require('gm');
 
@@ -40,6 +38,12 @@ var roleMapping = {
 };
 
 router.get('/', function(req, res, next) {
+
+  res.status(200).json([]);
+  return;
+
+  // FIXME TODO
+  
   var showActionForSpaces = function(err, spaceIds) {
     var userMapping = {
       '_id': 1,