FEATURE: Improving bookmarks part 2 -- Topic Bookmarking (#8954)

### UI Changes

If `SiteSetting.enable_bookmarks_with_reminders` is enabled:

* Clicking "Bookmark" on a topic will create a new Bookmark record instead of a post + user action
* Clicking "Clear Bookmarks" on a topic will delete all the new Bookmark records on a topic
* The topic bookmark buttons control the post bookmark flags correctly and vice-versa
Disabled selecting the "reminder type" for bookmarks in the UI because the backend functionality is not done yet (of sending users notifications etc.)

### Other Changes

* Added delete bookmark route (but no UI yet)
* Added a rake task to sync the old PostAction bookmarks to the new Bookmark table, which can be run as many times as we want for a site (it will not create duplicates).

test/javascripts/acceptance/topic-test.js.es6

@@ -333,3 +333,17 @@ QUnit.test("Quoting a quote keeps the original poster name", async assert => {
       .indexOf('quote="codinghorror said, post:3, topic:280"') !== -1
   );
 });
+
+acceptance("Topic + Post Bookmarks with Reminders", {
+  loggedIn: true,
+  settings: {
+    enable_bookmarks_with_reminders: true
+  }
+});
+
+QUnit.test("Bookmarks Modal", async assert => {
+  await visit("/t/internationalization-localization/280");
+  await click(".topic-post:first-child button.show-more-actions");
+  await click(".topic-post:first-child button.bookmark");
+  assert.ok(exists("#bookmark-reminder-modal"), "it shows the bookmark modal");
+});