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/importsongs.js

@@ -386,6 +386,7 @@
 			document.head.appendChild(style)
 		}
 		if(this.songs.length){
+			var length = this.songs.length
 			assets.songs = this.songs
 			assets.customSongs = true
 			assets.customSelected = 0
@@ -395,6 +396,7 @@
 				loader.screen.removeChild(this.loaderDiv)
 				this.clean()
 				new SongSelect("browse", false, this.songSelect.touchEnabled)
+				pageEvents.send("import-songs", length)
 			}, 500)
 		}else{
 			loader.screen.removeChild(this.loaderDiv)