Rename viewDiscussions => viewForum, viewUserList => searchUsers (#2854)

This naming is clearer as to the intended effect. Changes include:

- A migration to rename all permissions
- Updating the seed migration to use the original naming from the start
- Replacing usage of the old names with new names in code
- Throwing warnings when the old names are used.

js/src/admin/AdminApplication.js

@@ -58,7 +58,7 @@ export default class AdminApplication extends Application {
     const required = [];
 
     if (permission === 'startDiscussion' || permission.indexOf('discussion.') === 0) {
-      required.push('viewDiscussions');
+      required.push('viewForum');
     }
     if (permission === 'discussion.delete') {
       required.push('discussion.hide');

js/src/admin/components/PermissionGrid.js

@@ -100,11 +100,11 @@ export default class PermissionGrid extends Component {
     const items = new ItemList();
 
     items.add(
-      'viewDiscussions',
+      'viewForum',
       {
         icon: 'fas fa-eye',
-        label: app.translator.trans('core.admin.permissions.view_discussions_label'),
-        permission: 'viewDiscussions',
+        label: app.translator.trans('core.admin.permissions.view_forum_label'),
+        permission: 'viewForum',
         allowGuest: true,
       },
       100
@@ -121,11 +121,11 @@ export default class PermissionGrid extends Component {
     );
 
     items.add(
-      'viewUserList',
+      'searchUsers',
       {
         icon: 'fas fa-users',
-        label: app.translator.trans('core.admin.permissions.view_user_list_label'),
-        permission: 'viewUserList',
+        label: app.translator.trans('core.admin.permissions.search_users_label'),
+        permission: 'searchUsers',
         allowGuest: true,
       },
       100