Make SimpleLogger open;
Simplify PlatformLogger;
PlatformLogger on JVM now has `isColored` param and prints exception canonically;
Unify log format;

Improve toString of Active, Kick events,
Cancel Group when kicked,
Fix #319

修改图标

Use interface for JavaFriendly APIs;
Deprecate event responder in Bot in the favor of their member functions;
Deprecate `Bot.queryUrl(image: Image)`` in the favor of the extension `Image.queryUrl`