Custom scripting, #song=, translations

- A song can be linked directly by adding "#song=<id>" to the url, replace `<id>` with the id in the database, after loading it jumps immediately jumps to the difficulty selection
- Added tutorial translations
- Fixed song preview not playing
- Use text fallback for the logo when there are no vectors
- Increased combo cache by 1 pixel
- A custom javascript file can be loaded from config.json by defining "custom_js" value
- Added lots of events to help writing custom js files: `version-link, title-screen, language-change, song-select, song-select-move, song-select-difficulty, song-select-back, about, about-link, tutorial, import-songs, import-songs-default, session, session-start, session-end, debug, load-song, load-song-player2, load-song-unfocused, load-song-cancel, load-song-error, game-start, key-events, p2-game-end, p2-disconnected, p2-abandoned, pause, unpause, pause-restart, pause-song-select, game-lag, scoresheet, scoresheet-player2`
- Event syntax example:
```js
addEventListener("game-start", event => {
	console.log("game-start", event.detail)
})
```

public/src/js/session.js

@@ -30,9 +30,11 @@ class Session{
 			}else if(response.type === "songsel"){
 				p2.clearMessage("users")
 				this.onEnd(false, true)
+				pageEvents.send("session-start")
 			}
 		})
 		p2.send("invite")
+		pageEvents.send("session")
 	}
 	mouseDown(event){
 		if(event.target === this.sessionInvite){
@@ -50,6 +52,7 @@ class Session{
 			p2.send("leave")
 			p2.hash("")
 			p2.hashLock = false
+			pageEvents.send("session-cancel")
 		}else if(!fromP2){
 			return p2.send("songsel")
 		}