Issue #4277: add two system event "game_on_show", "game_on_hide" to cocos2d-html5
Merge branch 'develop-3.0' of git://github.com/cocos2d/cocos2d-html5 into Iss4277_FixBugsForV3.0

Conflicts:
	CCBoot.js
Issue #4277: remove index.html from Cocos2d-Html5
Merge pull request #1642 from dingpinglv/Iss4277_FixBugsForV3.0

Issue #4277: remove index.html from Cocos2d-Html5