Define the interface for mod to modify the stage.

[andy840119]

Some of the styles are affected by ruleset configuration and skin.
For example, DrawableLyric reads the fontInfo from ruleset config and applies the change directly.

After all style-related property should be adjust by command, should changed to:

1. create a default command for each stage info.
2. If want to override the default font, should create a mod that can read the ruleset configuration, and generate the command by the mod.