Add router.basePath config option for deployments at non-webroot

This is in preparation of configuring Vue with publicPath: "".

src/config.js

@@ -71,6 +71,9 @@ const DEFAULT_CONFIG = {
     reloadHistory: false,
   },
   primaryColor: "#3f51b5",
+  router: {
+    basePath: "/",
+  },
   selectedDevice: null,
   selectedUser: null,
   showDistanceTravelled: true,

src/router.js

@@ -1,12 +1,13 @@
 import Vue from "vue";
 import Router from "vue-router";
-import Map from "./views/Map.vue";
+import config from "@/config";
+import Map from "@/views/Map.vue";
 
 Vue.use(Router);
 
 export default new Router({
   mode: "history",
-  base: process.env.BASE_URL,
+  base: config.router.basePath,
   routes: [
     {
       path: "/",