refactor: started work on porting socket methods to write API [breaking]

The following socket calls have been removed:

* `posts.getRawPost`
* `posts.getPostSummaryByPid`

Two new Write API routes have been added:

- `GET /api/v3/posts/:pid/raw`
- `GET /api/v3/posts/:pid/summary`

public/src/client/topic.js

@@ -315,7 +315,7 @@ define('forum/topic', [
 			destroyed = false;
 
 			async function renderPost(pid) {
-				const postData = postCache[pid] || await socket.emit('posts.getPostSummaryByPid', { pid: pid });
+				const postData = postCache[pid] || await api.get(`/posts/${pid}/summary`);
 				$('#post-tooltip').remove();
 				if (postData && ajaxify.data.template.topic) {
 					postCache[pid] = postData;