Token auth (#434)

* Embed device platform information into token request

* Remove username and password from userProfile

* Display icon to show if profile has associated user token

* Remove username / password from login settings screen

* Refactor login procedure around token auth

* Refactoring

* Add profile login screen

- Username / password values are not stored
- Just to fetch api token

* Login with basic auth

* Pass profile to API when connecting

* Remove _BASE_URL accessor

- Fixes URL caching bug

* Add more context to login screen

* Add helper functions for unit tests

- Change default port to 8000 (makes testing easier with local inventree instance)

* api.dart handles basic auth now

* fix api_test.dart

* Further test improvements

* linting fixes

* Provide feedback when login fails

* More linting

* Record user details on login, and display in "about" widget

* Fix string lookup

* Add extra debug

* Fix auth values

* Fix user profile test

lib/settings/settings.dart

@@ -9,7 +9,7 @@ import "package:inventree/settings/about.dart";
 import "package:inventree/settings/app_settings.dart";
 import "package:inventree/settings/barcode_settings.dart";
 import "package:inventree/settings/home_settings.dart";
-import "package:inventree/settings/login.dart";
+import "package:inventree/settings/select_server.dart";
 import "package:inventree/settings/part_settings.dart";
 
 
@@ -51,7 +51,7 @@ class _InvenTreeSettingsState extends State<InvenTreeSettingsWidget> {
                   subtitle: Text(L10().configureServer),
                   leading: FaIcon(FontAwesomeIcons.server, color: COLOR_ACTION),
                   onTap: () {
-                    Navigator.push(context, MaterialPageRoute(builder: (context) => InvenTreeLoginSettingsWidget()));
+                    Navigator.push(context, MaterialPageRoute(builder: (context) => InvenTreeSelectServerWidget()));
                   },
               ),
               ListTile(