issue #2771:  add tag and enable functions to physics classes
Merge branch 'develop' of https://github.com/cocos2d/cocos2d-x into iss2771_physical
issue #2771:  refactor PhysicsTest
issue #2771:  move _physicsBody from sprite to node
issue #2771:  separate the PhysicsBody and the PhysicsShape.
issue #2771:  fix some bugs in PhysicsShape
issue #2771:  let PhysicsShape::create doesn't need to pass the PhysicsBody
issue #2771:  add PhysicsMaterial
Update .gitmodules, fix wrong reference of auto-generated.
issue #2823: firefox remote connection ok.
issue #2823: comment some test codes.
issue #2823: load js file in firefox.
issue #2823: firefox debugger step ok.
issue #2823: debugger loading js source with utf8 is ok.
issue #2823: Moving 'utf16to8' to DevToolsUtils.js and adding 'utf8to16' function.
issue #2823: Fixing mess code when modifying the value of variables which contains utf8 letters.
issue #2823: Removing unused codes in jsb_debugger.js.
issue #2823: Removing unused file 'main.debug.js'.
issue #2823: minor fix and logs.
issue #2823: Fix socket errors on WINDOWS.