Fix handling of contentScaleFactor != 1

fixes for Sprite, scale9Sprite, and LabelTTF.
performance improvement for contentScaleFactor fix in Sprite.draw
Merge remote-tracking branch 'upstream/develop' into contantScaleFactorFixes
Merge pull request #1033 from linshun/iss2580_v2.1.5

issue #2580: Merged  v2.1.5 to master branch
Merge branch 'contantScaleFactorFixes' of https://github.com/MarkEHenderson/cocos2d-html5 into ContentScaleFactorNotEqual1
Merge pull request #1036 from linshun/iss2580_v2.1.5

issue #2580: Merged plugin-x and some bug fixing to master branch
Test ContentScaleFactor NotEqual 1
Merge branch 'develop' of https://github.com/cocos2d/cocos2d-html5 into ContentScaleFactorNotEqual1
Fix handling of contentScaleFactor != 1
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