attachment download now works also in electron, added option to open the attachment

package.json

@@ -29,6 +29,7 @@
     "ejs": "~2.5.7",
     "electron": "^1.8.2",
     "electron-debug": "^1.5.0",
+    "electron-dl": "^1.11.0",
     "electron-in-page-search": "^1.2.4",
     "express": "~4.16.2",
     "express-promise-wrap": "^0.2.2",
@@ -45,6 +46,7 @@
     "jimp": "^0.2.28",
     "moment": "^2.20.1",
     "multer": "^1.3.0",
+    "open": "0.0.5",
     "rand-token": "^0.4.0",
     "request": "^2.83.0",
     "request-promise": "^4.2.2",