Merge pull request #1033 from linshun/iss2580_v2.1.5

issue #2580: Merged  v2.1.5 to master branch
Merge pull request #1036 from linshun/iss2580_v2.1.5

issue #2580: Merged plugin-x and some bug fixing to master branch
fixed #2380 updated reference of submodule
Merge pull request #1038 from dingpinglv/Iss2380_V215Release

fixed #2380 updated reference of submodule
Merge pull request #1037 from dingpinglv/ContentScaleFactorNotEqual1

Fix handling of contentScaleFactor != 1
fixed a bug of cc.Sprite that it's wrong when call _changeTextureColor function