UX: improvements to new dashboard

- remove inactive user report and replace with posts
- clean up internals so grouping by week happens on client
- when switching periods old report was not destroyed leading to bugs
- calculate trend based on previous interval ... not previous 30 days
- show percentages for mau/dau
- be more careful about utc date usage
- show uniqu and click through rate on search panel
- publish key of report with report so we only load the correct one
- subscribe earlier in channel in case of concurrency issues

test/javascripts/fixtures/posts.js.es6

@@ -0,0 +1,18 @@
+export default {
+  "/admin/reports/posts": {
+    "report": {
+      "type": "topics",
+      "title": "Topics",
+      "xaxis": "Day",
+      "yaxis": "Number of new posts",
+      "data": null,
+      "total": null,
+      "start_date": "2018-03-26T00:00:00.000Z",
+      "end_date": "2018-04-25T23:59:59.999Z",
+      "category_id": null,
+      "group_id": null,
+      "prev30Days": 0,
+      "labels": null
+    }
+  }
+};

test/javascripts/models/report-test.js.es6

@@ -60,4 +60,4 @@ QUnit.test("thirtyDayCountTitle", assert => {
 
   assert.ok(title.indexOf('+50%') !== -1);
   assert.ok(title.match(/Was 10/));
-});
+});