issue #2771: add class PhysicsDebugDraw
issue #2771: rename PhysicsWorld::create() to PhysicsWorld::construct(), fix some bugs
issue #2771: add pointQuery
issue #2771: edit assert message
issue #2771: change pointQuery implements
issue #2771:  add comment and improve API
issue #2771:  add comments
issue #2771:  fix bugs
Merge branch 'develop' of https://github.com/cocos2d/cocos2d-x into iss2771_physical
Merge branch 'iss2771_physical' of https://github.com/boyu0/cocos2d-x into iss2771_physical
issue #2771:  delete PhysicsSlidingJoint and PhysicsSpringJoint. add joint tests, fix bugs
issue #2771:  fix some api name and code style
fix bugs: delete initTest functions.
issue #2771:  change debug draw defines to class static const variable
HotFix: remove Mac platform Image::saveToFile assert
issue #2771:  fix indent
Merge pull request #4290 from boyu0/delete_initTest_in_testcpp

[ci skip]fix bugs: delete initTest functions in TestCpp.
Merge commit '0f509f7a739f245b63dd9590ba96b2600c803ec3' into iss2771_physical
Merge pull request #4275 from boyu0/iss2771_physical

[ci skip]issue #2771: physical
Merge pull request #4288 from nutty898/develop_nutty_modify_bugfixed

[ci skip]Develop nutty modify bugfixed