Add custom Don

- Registered users can customise the colour of their Don and it will appear for other players
- Bug fixes:
  - Add lyrics checkbox to admin page
  - 2P shows above "creative" or "with lyrics" labels
  - Prevent accidental alt and menu keyboard presses from triggering browser menus
  - Fixed mouse hitboxes on difficulty selection
  - Clean cached sounds and lyrics when another song is loading
  - Fixed debug jumping to the top-left of the screen when hidden
  - Fixed server volume not being applied to songs

public/src/js/main.js

@@ -80,6 +80,10 @@ var perf = {
 	allImg: 0,
 	load: 0
 }
+var defaultDon = {
+	body_fill: "#5fb7c1",
+	face_fill: "#ff5724"
+}
 var strings
 var vectors
 var settings