Add an `update_user_features` migration.

migrations/4_update_user_features.coffee

+Settings = require "settings-sharelatex"
+fs = require("fs")
+mongojs = require("mongojs")
+ObjectId = mongojs.ObjectId
+db = mongojs(Settings.mongo.url, ['users'])
+_ = require("underscore")
+BSON = db.bson.BSON
+
+handleExit = () ->
+	console.log('Got signal.  Shutting down.')
+
+process.on 'SIGINT', handleExit
+process.on 'SIGHUP', handleExit
+
+module.exports.migrate = (client, done=()->) ->
+	patch = {
+		$set: {
+			features: {
+				collaborators: -1
+				dropbox: true
+				versioning: true
+				references: true
+				templates: true
+				compileTimeout: 180
+				compileGroup: "standard"
+			}
+		}
+	}
+	console.log ">> updating all user features: ", patch
+	db.users.update {}, patch, {multi: true}, (err) ->
+		console.log "finished updating all user features"
+		return done(err)