Multiplayer improvements and reupload score on error

- In multiplayer you will play at the bottom if you joined second
- Add a dialog to song select that score has not been saved
- Uploads the score when logged in again
- Translate error messages from the server

public/src/views/login.html

@@ -2,9 +2,10 @@
 	<div class="view">
 		<div class="view-title stroke-sub"></div>
 		<div class="view-content">
+			<div class="error-div"></div>
 			<form class="login-form">
 				<div class="username-hint"></div>
-				<input type="text" name="username" required>
+				<input type="text" name="username" maxlength="20" required>
 				<div class="password-hint"></div>
 				<input type="password" name="password" required>
 				<div class="password2-div"></div>