Implement stage class as metadata in the karaoke beatmap #1755

What's will planning:

1. Layout will be the part of metadata in the karaoke beatmap, and will have following type of layouts:

   • Classic -> Current version .
   • Scrolling -> Might appear in the V2.
   • Animation -> Might appear in the V2 or later

2. Not recording time info in the Lyric class because the start time and the end time will be affected by the layout.

   • The start time and end time will not be saved in the layout metadata, or being calculated instead.

3. Re-define the roles:

   • Beatmap: record the supported layout type and it's info.
   • Hit object(Lyric): pure and most importand data, the data field should always useful and will not being replaced if display type changed.
   • Skin: give it an id, and it will return something like texture and shader effect.