revert download.py and delete submodule
remove submodule
Merge pull request #8127 from newnon/v3_precompiled_headers

Precompiled headers improvements
[AUTO][ci skip]: updating cocos2dx_files.json
[ci skip]
Merge pull request #8128 from CocosRobot/update_cocosfiles_1411527466

[AUTO][ci skip]: updating cocos2dx_files.json
add back config.json
adjust config
recheck download.py
add downloading prompt
add more prompt to debug
Merge pull request #8129 from andyque/fixSubmodule

remove submodule, use download.py instead