AddChild test fix

`sortAllChildren` should not be part of the test.
It is tested separatedly on another test
Adds better names to test

And new values for get(),add(),remove(),sort(),reorder()
objectComparisonLess -> nodeComparisonLess

and unified it.
No need to have 3 different copies.
The only copy is in CCNode.cpp
uses std::sort() by default
resets random seed before each test
adds two more perf tests

Node::addChild and Node::removeChild
add missing head
Merge pull request #3516 from minggo/perf_addchild_test_fix

Perf addchild test fix