Optional generation Preshared Key when creating a new client. (#140)

* Added support for Pre-shared Key.
Modified Create to generate a PSK should that be required.
Included Preshared key in Config/QR if it applies.
Show PSK on EditClient Page.

* Fix formatting on existing code.

* Remove unused err variable

ui/package.json

@@ -22,8 +22,10 @@
         "@smui/button": "^1.0.0",
         "@smui/dialog": "^1.0.0",
         "@smui/fab": "^1.0.0",
+        "@smui/form-field": "^1.0.0",
         "@smui/icon-button": "^1.0.0",
         "@smui/paper": "^1.0.0",
+        "@smui/switch": "^1.0.0",
         "@smui/textfield": "^1.0.0",
         "@smui/top-app-bar": "^1.0.0",
         "babel-jest": "^24.9.0",