Merge pull request #2315 from dumganhar/master

[TestLua] The menu item of Tests which is not supported will be disabled.
Merge pull request #2316 from dumganhar/master

fixed #2004: Adding UserDefaultTest for TestLua.
Merge pull request #2317 from dumganhar/master

fixed #2005: Adding CurrentLanguageTest for Testlua.
Add plugin code into cocos2d-x engine.
Submit the sample code HelloIIAP.
Reduce function call in nativeInitBitmapDC to improve performance.
Commit the tools for game developers.
Remove the environment config for plugin.
Merge remote-tracking branch 'upstream/master'
Merge pull request #2319 from natural-law/master

fixed #1471: Plugin system design.
Merge pull request #2318 from Yodesoft/master

Reduce function call in nativeInitBitmapDC to improve performance.