Add privilege level getters to Vuex.

* writeaccess: true if user can change data.
* adminaccess: true if user is an administrator.

lib/www/client/source/src/store/modules/user/getters.js

@@ -3,4 +3,12 @@ function user (state) {
   return state.user;
 }
 
-export default { user };
+function writeaccess (state) {
+  return state.user && ["user", "admin"].includes(state.user.role);
+}
+
+function adminaccess (state) {
+  return state.user && state.user.role == "admin";
+}
+
+export default { user, writeaccess, adminaccess };